Derry's walls were originally built by the Irish Society between 1613 and 1619. They were built with the intention of protecting the Scottish and English planters that had moved to Ulster as part of the Plantation of Ulster that had been established by James I. It was a direct consequence of the previous settlement being destroyed by Irish chieftain Cahir O'Doherty during O'Doherty's rebellion. As a result of the building of the city's defences by the Irish Society, which was a consortium of livery companies based out of the City of London, the city was officially renamed Londonderry in the 1613 royal charter. This is what has subsequently led to the naming dispute for the city and county of Derry/Londonderry.
The walls are at the centre of the historic city of Derry and within them are a number of Derry's most important landmarks including the Apprentice Boy's Hall and St. Columb's Cathedral.
The walls are about 1 mile in circumference and contain many of the city's most important landmarks. The entire length of the walls is fully accessible on foot. There are seven gates in total, four of which were built at the same time as the walls themselves and three were added later.
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.