Teeming with sea creatures of all sizes, shapes and colors, this giant fishbowl is the centerpiece of downtown Boston's waterfront. The main attraction is the three-story Giant Ocean Tank, which swirls with thousands of creatures great and small, including turtles, sharks and eels. Countless side exhibits explore the lives and habitats of other underwater oddities, as well as penguins and marine mammals.

Harbor seals hang out in an observation tank near the aquarium entrance, while the open-air Marine Mammal Center is home to northern fur seals and California sea lions. Visitors can watch training sessions where the pinnipeds show off their intelligence and athleticism. Note that some animal rights groups make a strong case that marine mammals should not be kept in captivity, no matter how classy their quarters.

The Shark and Ray Touch Tank recreates a mangrove swamp teeming with Atlantic rays, cownose rays, bonnethead sharks and epaulette sharks. Descend to the lower level to discover a room full of ethereal sea jellies. Most of the aquarium's 1st floor is occupied by an enormous penguin exhibit, home to more than 80 birds representing three different species. Six different tanks showcase the flora and fauna of the Amazon rainforest.

The 3-D Simons IMAX Theatre features films with aquatic themes. The aquarium also organizes whale-watching cruises. Combination tickets are available.