This, the third of the great South Kensington museums, stands behind the Natural History Museum in a far plainer building. It has loads of hands-on exhibits, with entire schools of children apparently decanted inside to interact with them; but it is, after all, painlessly educational. Highlights include the Launch Pad gallery, which demonstrates basic scientific principles (try the plasma ball, where your hands attract "lightning" -- if you can get them on it); Puffing Billy, the oldest steam locomotive in the world; and the actual Apollo 10 capsule. But don't be mistaken in thinking this is kids'-only territory -- there's plenty here for all ages. The latest and best offering for that is the Wellcome Wing, a space-age addition devoted to contemporary science, medicine, and technology, which also includes a 450-seat IMAX cinema. Note that there's a special charge for the cinema shows, and for the special exhibitions. COST: Free. Tube: S. Kensington.