Piscina das Marés

Piscina das Marés, meaning “tidal pools” in Portugese, is a saltwater pool just a short drive from Porto, Portugal. It is also a shining example of modernist architecture and an early work by the renowned Portuguese architect, Álvaro Siza Vieira. Despite its revered status in the architecture community, Piscina das Marés is first and foremost a public swimming pool, beloved by the local community who flock to it every year between the bathing months of June to September. In this way, it is also the greatest testament to Siza’s approach to architecture, one that holds the context of a design above a designer’s own ego.

Born in 1933 in Matosinhos, a region known for its fishing industry and proximity to the sea, Álvaro Siza Vieira was greatly influenced by his coastal upbringing. After graduating from the University of Porto's School of Architecture in 1955, Siza began his career under the mentorship of Fernando Távora, a prominent figure in Portuguese architecture. Távora instilled in Siza the importance of context, history and the vernacular architecture of Portugal, which features prominently in his work.



By the mid-1960s, Siza had begun to gain recognition for his work, most notably the Boa Nova Tea House, a stepped structure built into the coastline of Leça da Palmeira which caught the eye of the local council. Impressed by his ability to blend architecture with the natural landscape, plus his personal connection to the area, they entrusted him with designing a new public swimming facility built into the shoreline of Piscina das Marés.



Siza envisioned a space that felt like an extension of the natural shoreline, where built and natural environments could coexist.



The resulting concrete structure comprises two saltwater swimming pools – filled by the tide – alongside changing rooms, showers and a cafe. The existing topography dictates the design, as the facility is shaped around and set into rock formations, creating a seamless integration with the coastline, while concrete surfaces are treated to mimic the surrounding texture and colour. A minimalist aesthetic is employed throughout, with an emphasis on clean lines and the contrast between light and shadow. The layout is meticulously planned to provide clear views of the sea from every angle, with unobstructed sightlines and an undisturbed horizon.

The construction of Piscina das Marés took place during a period of significant architectural experimentation and innovation in Portugal, in which Álvaro Siza Vieira played a key role. The design reflects the modernist principles that were gaining prominence at the time – functionality, simplicity and a strong connection to the natural environment – while showing great reverence for the local tradition and culture. This approach has become synonymous with Siza – sometimes described as a “poetic modernist” – as he has continued to adapt construction methods and aesthetics to each project, as opposed to enforcing a singular, identifying visual language.



Since its completion, Piscina das Marés has been recognised as a masterpiece of modern architecture. In 2006, it was designated a National Monument of Portugal, highlighting its significance in the country's cultural heritage. The design of Piscina das Marés has influenced subsequent architectural projects that seek to harmonise built environments with natural settings. Siza Vieira's work is studied worldwide, serving as an example of how architecture can enhance and complement the natural world.



But perhaps more importantly, it remains a cherished swimming site, used regularly by the local community every bathing season in Portugal.