AHHAA (pronounced like 'aha') is the largest science centre in the Baltic states and genuinely excellent — the kind of hands-on science museum that makes adults feel as engaged as children. The permanent exhibitions cover physics, chemistry, biology, and technology through interactive installations. The centrepiece is the world's largest Hoberman sphere, which expands and contracts on schedule above the main floor.
The centre also has a planetarium, a 4D cinema, and temporary exhibitions on rotating scientific themes. Located on the edge of the old town near the river, it is a natural half-day destination if you are traveling with children or simply want a break from history museums. Estonian science education takes the place seriously — the facilities are impressive.