Oceanário de Lisboa

The Oceanário de Lisboa is consistently rated the best aquarium in the world, and the fact that it sits in a building designed to look like an aircraft carrier floating on a lagoon only adds to the experience. Built for Expo '98 — the world's fair that transformed Lisbon's derelict eastern waterfront into the modern Parque das Nações district — the Oceanarium was designed by American architect Peter Chermayeff, who had already built aquariums in Osaka and Baltimore. His concept was radical: instead of separating marine environments into discrete tanks, he created a single massive central tank holding five million liters of seawater, surrounded by four smaller habitats representing the Atlantic, Pacific, Indian, and Antarctic oceans.

The central tank is mesmerizing. Sharks, rays, tuna, and an enormous ocean sunfish (mola mola) glide past in an endless loop while you circle the tank across two levels. The sunfish alone is worth the visit — it looks like God started designing a fish and gave up halfway through, leaving a creature that is essentially a giant head with fins. The four surrounding habitats include above-water environments, so you can see penguins, sea otters, and seabirds in recreated coastal landscapes before descending to see the underwater side of the same habitats. It's one of the few aquariums that genuinely changes how you think about oceans.

In 2011, a second building was added to house temporary exhibitions, and the first major show was a collaboration with Japanese artist Takashi Amano, who created the world's largest nature aquarium — a stunning freshwater landscape in a 40-meter tank filled with 40 species of tropical fish and 46 species of aquatic plants. The Oceanário also runs extensive conservation programs, including breeding programs for endangered species and research partnerships with marine biology institutions. It handles roughly one million visitors per year, and the gift shop is strategically placed at the exit, which means a lot of Portuguese children go home with plush sharks.