Sky Pool, London

The Sky Pool hanging above you is a feat of engineering that originated in a conversation about a lack of space. When developers realized they could not fit a regulation-sized swimming pool on the rooftop of either individual building in the Embassy Gardens complex, they decided to connect the two structures instead. The result is a fifteen-meter-long transparent bridge that allows swimmers to travel between buildings while suspended one hundred and fifteen feet in the air. Because the pool had to be both sturdy and completely clear, the design team turned to material science typically reserved for massive aquarium tanks. The structure is built from solid acrylic panels that are up to three hundred and sixty millimeters thick. This material was chosen for its refractive index, which is nearly identical to that of water, helping the pool appear almost invisible to anyone looking through it from the ground. Building the pool required international coordination, with the acrylic components manufactured in Grand Junction, Colorado. Once completed, the structure traveled across the Atlantic Ocean on a cargo ship to reach London. It was then lifted into place with a tolerance of only thirty centimeters, settling into specialized steel tubs that allow the entire pool to slide slightly on bridge bearings to accommodate the natural sway and settlement of the two buildings it connects.