Because the Atlantic Ocean isn’t enough, the beach in Leça da Palmeira, Portugal, boasts two saltwater swimming pools built to blend seamlessly into the natural landscape. Husky rock formations frame each pool—one for kids, one for adults—making them look like little oases at the ocean’s edge.

In fact, the pools are lined, like any other, with plain old drab concrete. While clearly visible, the concrete fades into its rocky surroundings like some desert mineral, emphasizing the fluid relationship between nature and artifice. 

The swimmers, too, become part of the setting. Visitors enter the complex on a walkway that obscures the passing traffic and even mutes the ocean’s waves. Then, after leaving the changing rooms, they look toward the pools that seem almost to tip into the vast Atlantic, like they’re walking the world’s most peaceful plank.

Completed in 1966, the tidal pools brought major attention to a young Álvaro Siza Vieira, who is now one of Portugal’s most celebrated architects. Siza Vieira won architecture’s highest prize, the Pritzker, in 1992, and Portugal designated his tidal pools a National Monument in 2006.