Tidal pools of Leça de Palmeira, Saltwater swimming complex in Leça da Palmeira, Portugal

The Tidal Pools of Leça de Palmeira are a saltwater swimming complex on the Portuguese Atlantic coast, where concrete basins are set directly into natural rock formations. The structure descends in levels from the street down to the water's edge, with changing rooms built underground beneath the poolside.

Álvaro Siza Vieira designed the pools in 1960 and construction ended in 1973; the complex opened in 1966. A restaurant planned for the north side in 1961 was never built. The pools were classified as a National Monument in 2011 and added to Portugal's UNESCO tentative list in 2017.

The pools draw people from the surrounding area who come to swim in the Atlantic within a setting where concrete and rock meet without a clear boundary. The design blends so naturally into the coastline that it is hard to tell where the built structure ends and the natural rock begins.

The pools are open seasonally between June and September and are run by the municipal company Matosinhos Sport. The complex lies on the rocky outcrops along the Avenida da Liberdade, reached by a route framed in raw cement; the changing rooms sit in the support structures below the walls. The surface is bare concrete and stone, so footwear with grip helps on wet ground.

Not a single natural rock was removed to build the pools, as Siza Vieira designed the entire layout around the existing stone formations. The shape of each basin was determined by the rock already there, which is why no two basins look alike.