A turn-of-the-20th-century factory hall houses the Technik-Museum, an impressive and vast collection of locomotives, aircraft, old automobiles, and fire engines. Automatic musical instruments, historical dolls and toys, and 19th-century fashion are displayed in the Wilhelmsbau. Highlights of the complex are the 420-ton U-boat (you can go inside) and the massive 3-D IMAX cinemas. There is also an exhibition hall devoted to outer space. Allow at least three hours to visit this extensive museum, which covers several large buildings.