While the inside is certainly structurally interesting, it’s the exterior that fascinates passers-by as they make their way down the highways of Barcelona. Torre Agbar, BarcelonaThe first skin that covers the concrete structure is a layer of polished aluminum in blues, greens, and grays. The second skin, which adds an iridescent sparkle to the building, is made up of 59,619 sheets of clear glass.

There are 4,400 windows accompanied by louvers that tilt in various directions to block out any direct sunlight. At night, the tower becomes yet more magnificent, with 4,500 yellow, blue, pink, and red lights illuminating the exterior.

Twenty-eight of the buildings thirty-four floors are currently used for offices and an additional three house the technical components of the building. A cafeteria occupies another entire floor, another boasts conference rooms, and one floor in the tower offers an observation area. Four subterranean floors contain an auditorium and parking facilities.