The watchtower in Proença-a-Nova | Álvaro Siza Vieira

The watchtower in Proença-a-Nova (2018–21) is powered by solar panels and rises at the summit of a mountain range called Serra das Talhadas. It might only be 16 meters tall, but it sits 616 meters above sea level, overlooking the 50-million-year-old quartzitic crests of the surrounding geopark. This tower is meant to prevent the spread of wildfires, besides also working as a belvedere at the summit of an ambitious rock-climbing trail. Álvaro Siza composed the watchtower with squared overhanging slabs and rounded corners. The floor plan distils the structure to its most essential shape: a cross grid, not unlike the neighbouring crucifix.