This modern museum in the Fort George District provides an excellent overview of the story of Belize. Housed in the country's former main jail (built of brick in 1857), the museum preserves one cell in its original state, complete with inmates' graffiti; if you thought your hotel room was cramped, think again! Fascinating historical photos and documents bear testimony to the colonial and independence eras, and the destruction wrought by hurricanes.
The Maya Treasures section, upstairs, is rather light on artifacts (most of Belize's finest Maya finds were spirited away to other countries) but there are some impressive examples of Maya jade, as well as some ceramics and sculpture. You'll also find plenty of informative models and explanations of the major Maya sites around the country. Other sections of the museum are devoted to Belize's highly colorful postage stamps, and its insect life, with full detail on the disgusting manner in which the human botfly uses living human flesh to nourish its larvae. The museum also has a good little gift shop.