Not just a stun­ning spot for a dip, Pisci­na das Marés (in Leça da Palmeira, on the out­skirts of Por­to) is also an archi­tec­tur­al mar­vel. The angu­lar con­crete frame was an ear­ly work by star­chi­tect Álvaro Siza. In fact, Siza grew up ten min­utes away in Matosin­hos – which might explain the inti­mate way that the pools and ramps of the Pisci­na das Marés melt into the rocky Atlantic coast.