Lisbon Oceanarium. Man admires the main tank at the Lisbon Oceanarium in Portugal, the largest aquarium in Europe. The Oceanarium is the centre- piece of Expo 98, which is themed around the oceans. The tank is viewed through 7 metre high windows made from 30 centimetre thick acrylic glass. The glass is curved for strength, which also minimises light diffraction, giving an undistorted view of the insoceanins. At the corners of the tank are habitats representing the Atlantic, Antarctic, Pacific and Indian Oceans. More glass separates these from the main tank and helps to maintain their varied conditions. The Oceanarium holds over 15,000 animals from 200-300 species.