In Sunny cartagena, a futuristic mass of steel and polycarbonate hovers over the ancient Roman ruins of Molinete Park. “Our idea was to have something like a cloud,” says Nicolás Maruri, a principal of the Madrid architecture firm Amann-Cánovas-Maruri, which designed the canopy. The architects also installed an elevated deck below, which provides views over a Roman bath, a forum – and a house decor­ated with ancient wall paintings.

The project is part of a long-running urban renewal initiative that has transformed a formerly rough district in the Spanish city into a popular destination. Sixty years ago, “This was where all the prostitutes were,” says Maruri. “It was the worst place in the city.” His firm has a rich history with the site. Nineteen years ago, it won a competition to prepare a 40,000-square-metre master plan to modernize the area. It has since completed a bold health care centre, and is in the midst of several other local projects. Meanwhile, archaeologists were seeking funding for a dig that would expose the Roman ruins they knew lay beneath some small houses (which have since been removed). As part of their vision, the architects proposed a covered museum, with the city above. Yet opposition from residents buried that project. “They wanted something more like Pompeii – an open archaeological site,” Maruri explains.

The archaeologists finally began to dig a few years ago and discovered the wall paintings. They determined that the find required protection from the sun and rain, which negated the idea of a completely open site. So they enlisted Amann-Cánovas-Maruri to build a visually arresting protective layer. The resulting structure represents a middle ground of sorts: an open-air museum beneath a stunning origami cloud. With perforated steel cladding above and a ceiling of poly­carbon­ate ­panels below, the 1,847-square-metre canopy allows daylight to filter in while protecting the ruins from the harshest elements. It also evokes a stark contrast between the site’s past and its future. “You always have this fight between the architects who want to have a city, and the archaeologists who want to preserve history and remains,” says Maruri. The citizens of Cartagena now have the best of both.