Brave slackliners have been pictured walking the ropes above Rio de Janeiro, Brazil on August 15, 2016, with the half a mile drop showing the city in all its glory. The stunning shots show the daredevils tread across an eighty-two-foot-long high line on Pedra da Gvea mountain with an amazing sunrise illuminating the city landscape behind. (Photo by Rafael Moura/Caters News Agency)

A workman takes a siesta on a girder during the building of Radio City, the city of New York spread out below. (Photo by General Photographic Agency/Getty Images). Circa 1933

The "Square Head" is a sculpture by the french artist Sacha Sosno, and it is also the very first giant sculpture to have been transformed in a habitable building.

The Clementinum (Klementinum in Czech) is a historic complex of buildings in Prague. Until recently the complex hosted the National, University and Technical libraries, the City Library also being located nearby on Mariánské Náměstí. The Technical library and the Municipal library have moved to the Prague National Technical Library at Technická 6 since 2009. It is currently in use as the National Library of the Czech Republic. In 2005, the Czech National Library received the UNESCO Jikji prize (Memory of the World).

In this photo taken Sunday, October 5, 2014, a library official shows a 13th-century German prayer book containing the earliest evidence of the Yiddish language, at Israel's National Library in Jerusalem. This week, Israel's National Library gave The Associated Press a rare peek at a selection of rare historical manuscripts in its collection. (Photo by Sebastian Scheiner/AP Photo)

A worker pauses for a sandwich, resting on a girder during the construction of a skycraper. (Photo by Hulton Archive/Getty Images). Circa 1930

Battersea Power Station. The chimney rims are thinner on top than you might expect. (Photo by Bradley L. Garrett)