Piscina das Marés

Álvaro Siza built the Piscina das Marés between 1959 and 1966, early in his career and in his home town, and it is among the most studied pieces of twentieth-century Portuguese architecture. The design refuses to announce itself: from the coast road there is only a low concrete wall, and the building is below road level, so bathers walk down a ramped concrete passage that turns, narrows, hides the sea entirely and then releases it all at once at the far end. The pools themselves are formed by concrete walls linking existing rock outcrops, filled with seawater, so the boundary between built and natural is deliberately unclear. It was restored in the 2000s under Siza's supervision and is a national monument. It operates as a public swimming facility in summer, which is the correct way to see it - not as a monument but full of families.

What you actually see

• The concealed entrance - a building below road level revealed only on the walk down.
• The ramped passage - a route that hides the sea and then opens it at once.
• The pools - concrete walls joining existing rock outcrops, filled with seawater.
• The working use - a public pool full of families, not a preserved monument.

When to go

June to September, when the pools operate. Two to four hours. Outside the season the structure can be seen from outside but not entered.

Honest expectations

It opens only in summer - out of season the gates are shut. Cold Atlantic seawater. It is a working municipal pool, so it is crowded on hot days and the architecture competes with families. Concrete surfaces get hot underfoot.

Nearby

The Boa Nova tea house, also by Siza, is a short walk north; Matosinhos is south.