Entertaining kids on hot or rainy days is no problem at this expansive museum, spread on four floors with 500 exhibits, a whopping 70 percent of them interactive. Children can learn about light, sound, electricity, magnetism, transportation, math, communication, life sciences, energy efficiency, food science, and more, all through fun activities like driving a car simulator, testing their knowledge of energy consumption in the average kitchen, comparing models of  human embryos through various stages of development, playing with puzzles and optical illusions, viewing themselves through various mirrors, creating bubbles, and more. Grownups can also get in on the action, especially the fitness area that lets visitors test balance, endurance, and more. Allow at least three hours here. If you don't have kids or yours are teenagers, I'd opt for the museum of history across the plaza.