The largest aquarium in London is located in the County Hall, the former seat of the Greater London Council.
It is divided into several sections, each presenting a different environment. There's the Ocean Tunnel allowing you to pass through a glass tunnel and see the fish swim all around you, or the so-called Shark Walk if you feel like walking over a glass window while sharks swim right under your feet. A new exhibition dedicated to penguins was opened quite recently. There are more than 500 species in total.
Check the official website for talks and feeding times, you can learn many interesting facts about your favourite animal here.