1. An introduction to the Spanish archaeological landscape and urban archaeology

Spain, a country of unparalleled historical richness, is home to an exceptional heritage that tells us the story of millennia-old civilisations. From the prehistoric vestiges of the first communities that inhabited Iberia, to traces of contemporary cultures, the abundance of archaeological sites reveals the cultural diversity and complexity of human evolution.

This rich, abundant and diverse heritage that appears across Spain in all its variants, terrestrial and underwater, includes cultural landscapes telling us about the beginnings of the industrial and postwar societies. This abundant heritage is often scattered and faces the challenge of balancing conservation with necessary urban and infrastructural development.

Although a fairly high percentage of these archaeological remains is found in rural areas, another not inconsiderable percentage is located in urban areas, bearing witness to the long history and origins of many Spanish cities. For this reason, so-called preventive archaeology has in recent years played a key role in the sustainable management of Spanish archaeological heritage in the context of major public works and investment. However, a role in management archaeology (Martínez Díaz and Querol 2013), which is crucial to ensure the legacy of this heritage for future generations, had not been developed in Spain until very recently, at least not in a comprehensive manner.

From the Spanish legislative perspective, in addition to the volume of archaeological heritage that has to be managed, there is an extra difficulty, because of the complex framework of competences within which this management must operate. Spain is one of the most decentralised countries in the world, which means that, regarding the management of archaeological heritage and in relation to major urban and infrastructural works, the relevant competences are generally assumed by each of the 17 autonomous communities and their respective municipalities (of which there are more than 8000). From the state's perspective, the national law on cultural heritage (Law 16/1985) determines that the state, through the Ministry of Culture, is competent in only a few cases: illicit trafficking, looting, if expressly mentioned, or on land assigned to public services managed by the state administration. This means that the state, through the Ministry of Culture, is responsible for authorising archaeological control and monitoring projects within major investment works, normally affected by services of general interest, such as those that occur for state roads, hydrographic confederations, army and defence areas, national stations and railway services throughout the region, as well as airport areas, in addition to all state public properties.

With this complex landscape in mind, the following is a brief review of some of the milestones in urban archaeology, preventive archaeology and management archaeology that show, not only the evolution of archaeological practice in the context of major construction works, but also examples of various solutions that can combine the preservation and enhancement of archaeological heritage with urban development.

2. The beginning: managing the growth of heritage cities, and some historical examples

As a curiosity and to provide a clear example of the evolution of preventive and urban archaeology in Spain, the case of Mérida will be briefly analysed. Mérida is a small city located in the south-west of Spain, capital of the autonomous community of Extremadura. During the Roman Empire it was the capital city of the province of Lusitania, and today it is considered one of the best-preserved Roman cities in the world, being a United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage site since 1993.

Figure 1 shows one of the first photographs of Mérida's Roman theatre, dating from the time of Augustus. This very damaged space was known as 'The Seven Chairs', alluding to the only structures then visible and known from the theatre, the summa cavea, after centuries of abandonment and disuse. As part of the urban development of the city in the early 20th century, archaeological excavations began in 1910, led by a famous Spanish archaeologist, José Ramón Mélida, with the subsequent reconstruction of the front of the theatre, applying an archaeological methodology that would now be questionable, but which was within the praxis of the time. In fact, a 'free' reconstruction was made, which was dismantled in the 1960s and rebuilt again, giving rise to the current appearance of the theatre (Mélida 1910; Almagro Gorbea 1988a; Blázquez 1993; Mateos Cruz 2001; Fernández 2018a; López 2021a). Focusing on its enhancement and a coexistence between the ancient and contemporary cities, in 1933 it had already been decided to recover its original function as a theatre, with the inception of an annual celebration that has continued since then and is now the Classic Theatre Festival of Mérida, which in 2024 celebrated its 70th anniversary.

In Figure 2 it is possible to see the current state of the theatre and its layout, very close to the amphitheatre and alongside the rest of the site of the ancient Roman city. Both spaces are just a few steps away from the current city and, specifically, from the National Museum of Roman Art, a museum managed by the Ministry of Culture that houses one of the most important archaeological collections from the Roman period in Spain.

Spanish museums are situated in locations where archaeological remains have been discovered more frequently, either as a result of new building construction work, in the case of new museums, or the remodelling of museums located in historic buildings. Considering the National Museum of Roman Art in Mérida, the construction project for the building itself foresaw the need to integrate the archaeological remains that were revealed within the museum area (Moneo 1993; Mateos Cruz 2010; Sabio González and Barrero Martín 2012; Fernández 2018b; López 2021b).

The museum was inaugurated with a monographic space, known as the crypt, dedicated to the archaeological site discovered there. This is very important, because the remains allow us to understand and contextualise this part of the ancient Roman city, within which the new city is growing. For example, the remains of the aqueduct of San Lazaro, one of the two that supplied water to the city, several sections of the road that connected Augusta Emerita with the city of Corduba, several residential areas located outside the walls, and part of a necropolis, are visible today (Nogales Basarrate 2008; Rodríguez 2015).

To improve the accessibility of the space, improvement works are currently being carried out, including preventive archaeological surveys. Moreover, the museum is working on a new extension that will culminate in an annex to the main building, where new archaeological remains that have appeared will also be curated.

3. An example of peaceful coexistence: Ibiza, a paradigm of contemporary preventive archaeology and large infrastructural requirements

Besides museums, other spaces where management archaeology often has to intervene to establish a peaceful coexistence between infrastructural needs and the protection and enhancement of archaeological heritage, are touristic and infrastructural spaces, especially in a country like Spain.

Some of the best, and more complex, examples where harmony has been achieved between urban development and the enhancement of archaeological heritage, are airports. Perhaps more than with other large public infrastructures, meeting the planning needs and requirements of public interest objectives is a priority for this type of construction, including the preservation of our cultural heritage. Although this aim has not always been understood and is still sometimes hard to achieve today, even with the enormous budgets and resources invested in this type of project, we should not forget that the conservation of, access to and enjoyment of cultural heritage is a constitutional right for Spanish citizens, and a duty for the public authorities.

Focusing in particular on the aerial infrastructure in Spain, regulations for the management of airports in general have established the need to create a master plan that defines management and development guidelines and takes into account, among other factors, the impact on protected elements, such as archaeological heritage.

Considering the example of Ibiza, one of the four islands that forms the archipelago of the Balearic Islands, off the east coast of Spain, this island is an important historical site not only for Spanish archaeology, but also for understanding the development of maritime trade in the Mediterranean and the evolution of the different cultures that flourished and prospered there (Almagro Gorbea 1967; Costa and Fernández 1997; Costa et al. in press). Of particular interest are the archaeological remains from Phoenician and Punic times, given that the island of Ibiza became a strategic enclave both in terms of resources and raw materials, as well as for the control of trade routes, as evidenced by exceptional archaeological sites such as Puig des Molins, sa Caleta and Es Culleram, among others. The testimonies of the Phoenician-Punic culture in Ibiza became the true protagonists in the expansion and improvement works of the island's international airport, which has been underway since 2018.

Ibiza International Airport is in the municipality of Sant Josep de sa Talaia, in the south of the island, approximately 7.5 km from the capital. It was inaugurated in 1966, at a time when, although the archaeological importance of the Ibiza was already known, heritage impact studies, particularly archaeological studies, were not only not the order of the day, but neither the sensitivity nor the awareness of heritage conservation was the same as today, especially when the major priority was to create a large infrastructure to improve the national and international coverage of air connections, both for freight and to promote tourism in Spain.

Today, however, awareness and sensitivity to archaeological heritage has changed for the better, among both the public administration and construction promoters, architects, engineers, and, in general, companies and workers dedicated to construction, as well as among citizens themselves. In this sense, and from a purely regulatory point of view, in addition to Spanish cultural heritage regulations, environmental impact studies are tools that, although of limited effectiveness, have brought about substantial changes in planning and determining the limits and needs of these types of projects in areas with heritage potential.

The general rule is that that, when faced with today's contradiction of development and preservation, the appropriate solution is to modify the original project sufficiently to eliminate or at least greatly minimise any risk to the heritage. However, this is not always possible. It should be borne in mind that, in most cases, public works in Spain are designed with the aim of providing the necessary public infrastructure to meet and cover needs related to public interest and social welfare. Therefore, on some occasions it is necessary to opt for strategies that can satisfy both parties as much as possible. To this end, it is crucial prior evaluations are carried out, to discern not only the real possibilities of partial or complete modification of the project, but also the social benefit of whether or not the archaeological remains are fully preserved. In other words, the importance of the archaeological remains in relation to the public service provided by the project must be assessed together, although this is not easy to evaluate. In any case, the decision is not in the hands of the promoter of the project, but of the competent public administration, and always with the technical and scientific advice of the archaeologists themselves, whose presence is mandatory in any construction project on a site with heritage potential.

With this in mind, and coming back to Ibiza airport, nowadays the legal framework has established the need to develop master plans for each airport to consider, among others, construction projects that will take place in subsequent years and that could affect the airport's environment. The current master plan for Ibiza airport was drafted in 2010, indicating the existence of 29 heritage assets and 4 archaeological sites. In the following years, several archaeological interventions, mainly prospecting, were carried out to complete the preliminary studies, locating three other areas with a concentration of archaeological material, mainly Roman and Punic, identified with the site names of Can Ribes, Can Ribes II and Can Bassetes. The interventions not only provided new archaeological evidence, but proved connections between those archaeological sites, which started to be considered as a single cultural unit (see below).

At the start of the airport expansion works, the remains of a hitherto unknown villa from the Roman and Byzantine periods were discovered at the very beginning of the archaeological research. Because of the importance of the find, it was decided to change the construction project and preserve the remains, although in this case it was not possible to place them in a museum in situ, as they were located in a service area of the airport (Villa González in press b) (Figure 3).

Another important archaeological discovery in the context of these airport expansion works took place at the aforementioned Punic site of Can Ribes II. The start of the archaeological works coincided with the COVID 19 pandemic, providing a unique opportunity to implement archaeological research without restricting the operation of the airport. This unexpectedly allowed a major archaeological excavation to be carried out. The remains found confirmed not only the importance of the site, but also that the apparently scattered remains actually formed one site, called Can Ribes II. On a scientific level, the excavations allowed the documentation of a pottery production workshop, a large wooden building, and the remains of a building probably dedicated to worship, all dating from around the 3rd–2nd centuries BC (Villa González in press a).

As the finds were located in the area of the airport runway, it was not possible to enhance the site in situ, and it was decided to cover and conserve the remains with geotextile and sand layers, with one exception: the engraving of a ship (Figure 4), which was located in a cistern and to which it was considered necessary to gain access. A laser scan of the engraving and a plaster cast were also made.

The discovery of this cistern, in an area close to the possible pottery workshop, is explained by the need for water sources in this type of workshop and, in fact, the excavations located several wells. The cistern has a rectangular floor plan and is bottle-shaped, with a wider base than the top. A relationship between the cistern and the temple cannot be ruled out, given its nearby location, and would explain the discovery of a votive altar in the fills (Villa González in press b).

Together with the altar, a series of ceramic remains was also found, with a particularly abundant 'fish dish' typology of dishes, characteristic of the 3rd–1st century BC, as well as various types of amphorae, the Punic-Ebusitan typology being particularly abundant, produced between 250 and 120 BC. These finds are relevant because they are possibly linked to production by the pottery workshop nearby, which, in light of the finds, could represent a semi-industrial activity with a clear commercial purpose. In addition, it is known, thanks to the discoveries at the Can Bassetes site (see below), that vines were grown on the land next to the workshop and the temple, from which wine was produced and transported in the amphorae (Villa González in press a). If these findings are connected with the Sa Caleta site, they can be linked to maritime trade routes in the area.

In fact, the engraving also provides interesting information about these possible trade routes. The depiction seems to show the hull of a ship, along with part of the sails and what may be interpreted as a fishing net. Naval engineering was one of the great Phoenician-Punic contributions to the Iberian Peninsula. This discovery is particularly important because depictions of boats from pre- and protohistory are very rare, and seldom have a clear archaeological context (Almagro Gorbea 1988b; Dams and Dams 1984). According to the studies carried out so far on this engraving (Villa González in press a), it seems that the image could correspond to a small type of boat used for both fishing and the transport of small goods and even people over short-distances by coastal navigation (Casson 1971; Guerrero Ayuso 1993, 2006, 2010; Mederos and Escribano 2008; García Cardiel 2013; Rey Da Silva 2014).

Finally, the expansion and improvement works at the airport also included extensions to the parking areas. Soil removal associated with these construction works revealed archaeological remains, which in this case confirmed the existence of cultivation ditches, possibly for vines (Figure 5) (Marlasca and López 2006) associated with the archaeological site of Can Bassetes. In this case, a mixed solution was adopted: keeping the cultivation trenches under the new construction and removing only those trenches that were above the construction level. This solution, although not ideal, was feasible, as there are abundant remains of similar typology and state of preservation in other parts of the island (Marlasca and López 2006).

Although it was not always possible to enhance the value of the remains that emerged during the expansion works of the Ibiza airport by preserving them in situ, an alternative was found, close to the site of discovery. In 2022 AENA, the agency responsible for the management of Spanish airports, in collaboration with the Ministry of Culture, set up a small exhibition space at Ibiza airport that would allow visitors to understand the historical site on which it was located. Additionally, the exposition shows how the government manages the coexistence of archaeology and public investment projects.

The exhibition, entitled 'Ibiza: meeting point since ancient times' consists of three showcases (travel, triad and spirituality) and a video projected on a giant screen that explains the various excavations carried out in recent years and their main findings. In 2022 Ibiza airport welcomed more than 8.2 million travellers. Taking into account the fact that the exhibition is located in a strategic place that every passenger must necessarily pass through, its creation means it has the potential to let all the travelling public know how important archaeology is to understand the island they are visiting.

In any case, the experience of Ibiza airport shows how archaeological management and coordination between all the actors involved in the development of large urban infrastructures makes it possible to find various solutions to different challenges, with the common aim of promoting the conservation and enhancement of the archaeological heritage.

To conclude, and as a recap, we have briefly discussed the main strategies, past and present, for the management of Spanish archaeological heritage in the context of public works. In short, knowledge of the terrain where major public works is to take place is crucial, to be able to manage the project's objectives, both in terms of deadlines and economic costs, alongside the presence of archaeological remains. This knowledge arises from bringing together past archaeological research and documentation with specific surveys of the sites that are going to be affected by the project.

Regarding the future, it should be noted that the Ministry of Culture is currently working on the creation of the first National Archaeology Plan, which aims to establish best practices in archaeological management at a national level. One of the chapters will specifically focus on management and good practice in preventive and urban archaeology, with the aim of creating a common and shared framework, as a cross-stakeholder strategy, which will hopefully lead to better management of the archaeological heritage in Spain.