Llac CosmoCaixa

You don’t come to the upper reaches of Sarrià-Sant Gervasi for the cheap beer or the beach. You come here to escape the humidity and the relentless, soul-crushing hum of the city center. Up here, leaning against the foothills of Tibidabo, sits CosmoCaixa—arguably the best science museum in Europe and a masterclass in how to make learning feel like something other than a chore. But before you descend into the subterranean depths of the museum, you have to deal with the Llac CosmoCaixa, the massive outdoor pond that anchors the Plaça de la Ciència.

First impressions? It’s a collision of worlds. On one side, you’ve got the Ampar de Santa Llúcia, a gorgeous 1904 Modernist brick building that used to be an asylum for the blind. On the other, a brutalist, glass-and-steel temple to human curiosity. The lake sits right in the middle, a flat, reflective plane that mirrors the clouds and the looming silhouette of the Sagrat Cor church way up on the mountain. It’s not just a decorative pond; it’s an interactive playground for anyone who hasn’t had the curiosity beaten out of them by adulthood.

This is one of the best things to do in Barcelona with kids, but don’t let that scare you off. The Llac is home to a massive Archimedes’ screw. You’ll see kids—and plenty of grown-ups who should know better—frantically cranking the handle to lift water from the pond into a series of troughs. It’s physics in its rawest, most satisfying form. Nearby, the Ictíneo II, a faithful replica of Narcís Monturiol’s 19th-century steam-powered submarine, sits like a steampunk dream. It’s a reminder that Barcelona has always been a city of inventors, dreamers, and people who weren't afraid to sink to the bottom of the ocean just to see what was there.

The atmosphere here is different from the Gothic Quarter. It’s local. It’s the sound of Catalan families on a Sunday morning, the smell of clean mountain air, and the occasional screech of a green parrot overhead. There’s a sense of space that you just don't get down by the port. You can sit by the water, watch the light shift across the glass facade of the museum, and actually hear yourself think. It’s a rare thing in this city.

Is CosmoCaixa worth it? Absolutely. Even if you never set foot inside the Flooded Forest or the Planetarium, the plaza and the lake are worth the trek. The honest truth, though, is that it’s a bit of a hike to get here. You’re going to have to navigate the FGC trains or a series of buses, and if you’re coming from the beach, it’ll feel like an expedition. It can also get loud—school groups descend on this place like locusts during the week, turning the serene physics lesson into a chaotic scramble of backpacks and high-pitched shouting.

But go late in the afternoon. When the sun starts to dip behind Tibidabo and the school buses have all cleared out, the Llac CosmoCaixa becomes something else. It’s a quiet, reflective corner of a city that rarely stops to reflect. It’s a place that respects your intelligence while acknowledging that, deep down, we all just want to turn a crank and see what happens. It’s honest, it’s beautiful, and it’s one of the few places in Barcelona that feels like it belongs entirely to the people who live here.