Museum der Illusionen

Vienna's mind-bending Museum of Illusions, opened in 2017, confounds your senses through its 40 interactive optical illusions and installations. They include stereograms (3D pictures with 'hidden' objects), tilted rooms, mirages, a giant kaleidoscope, an infinity room, and a tunnel with spinning images on the walls that make it impossible to keep your balance (despite the central walkway not moving). It's fascinating for kids and adults alike.