Las Setas is Jürgen Mayer’s timber waffle over a Roman archaeological site in Seville, and it’s one of the largest wooden structures in the world.

Seville tore down its market hall in 1973 and started digging a parking garage. Crews hit Roman ruins, work stopped, and the plaza sat as a hole for thirty years. A 2004 competition asked for something that covered the dig and gave the neighborhood its square back. Mayer’s answer: six parasols of laminated birch, 85 feet up, waffled into a canopy you walk across. It came in years late and roughly twice over budget, and Sevillanos still argue whether it belongs in a medieval center. They call it Las Setas, the mushrooms, and use it anyway — ruins in the basement, market at ground level, rooftop promenade above the rooftops.