On a budget, weigh it — NEMO Science Museum isn't cheap for what it is.
€17.50 (free under 4); rooftop free
The city's best rainy-day move with kids — everything is interactive, experiment-driven, and easy to lose hours in. The catch: it's pitched squarely at families, so adults without children will find it loud and basic, and the rooftop (with its great view) is free without a ticket.