It may sound like something out of a super-hero cartoon, and indeed the Aqua Dome, covering almost 500,000 square feet in Austria's Tyrol region, has an otherworldly design. An indoor pool sits behind massive crystal windows, while outdoor bowl-shaped ones course with water from thermal springs. One even features underwater lights and music. Elevated on stems-imagine something like giant martini glasses-the pools are connected by a glass cone-shaped building, while a lazy river wraps around them. Set amid farmland, the contemporary hotel was built in a combination of wood and stone, and when you look up from its solariums and terraces the peaks of the Ötztal Alps loom above.