The Koppelpoort is a medieval gate in Amersfoort. The gate was built between 1380 and 1425 as part of the second city wall. The whole wall was completed around 1450. The gate was attacked in 1427 during the siege of the city, but this attack was repelled.
The gate was opened and closed every day by the appointed 'wheel-turners'. A minimum of twelve wheel-turners were collected morning and evening by several guards. It was an extremely dangerous task; if they did not begin walking simultaneously, then one could fall, dragging the rest along with often fatal results. Before the gate could come down, it had to be raised, to pull out the iron pins that held it in place. Only then could it come down. While the gate was going down, walking in the wheel grew ever easier and faster, and many people stumbled and broke their limbs. The koppelpoort was also never breached.
The Koppelpoort was given its current appearance during the restoration by Pierre Cuypers in 1885 and 1886. Among other things, Cuypers removed a step between the two gates and replaced it with a slope.
The latest restoration was completed in 1996. It was carried out very cautiously, and with respect for the old building materials.
References:The Clementinum 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.
Its history dates from the existence of a chapel dedicated to Saint Clement in the 11th century. A Dominican monastery was founded in the medieval period, which was transformed in 1556 to a Jesuit college. In 1622 the Jesuits transferred the library of Charles University to the Klementinum, and the college was merged with the University in 1654. The Jesuits remained until 1773, when the Klementinum was established as an observatory, library, and university by the Empress Maria Theresa of Austria.