It’s hard not to shudder when you catch sight of a shark swimming above you, with its wide-toothed grin – but this 80m shark tunnel at Barcelona's aquarium is an experience not to be missed. One of Europe's largest, this aquatic attraction has the world’s best Mediterranean collection, as well as fish from all over the world, from the Red Sea to the Caribbean and the Great Barrier Reef. An incredible 11,000 creatures of 450 species call this aquarium home.