Second largest aquarium in Europe: Lisbon Oceanarium

LISBON, PORTUGAL - MAY 28: Atlantic puffins (Fratercula arctica) are seen as people visit the Lisbon Oceanarium (Oceanario de Lisboa) the second largest aquarium in Europe and is home to around 16,000 marine creatures from 450 different species, in Lisbon, Portugal on May 28, 2025. Opened in 1998 as part of the Expo '98 World Fair, the aquarium features a main tank with a capacity of 5 million liters, housing sharks, penguins, and tropical fish. Attracting great interest from both local and international tourists throughout the year, the facility offers a unique opportunity to closely observe underwater life. (Photo by Didem Mente/Anadolu via Getty Images)