Ratiaria, originally conquered by the Dacians and later by the Romans, was known for its gold mine possibly exploited by Thracians. The Romans became involved around 75 BC, and by 29 BC, Ratiaria was a fortified city. Under Augustus, the Romans officially conquered the region, organizing it into the province of Moesia. Ratiaria became a key station with a legionary fortress and fleet. After the division of Moesia in 86 AD, it became the capital of Upper Moesia.
Legio IV Flavia Felix was stationed here until the conquest of Dacia (101-106 AD). Afterward, Ratiaria became a colonia named Colonia Ulpia Traiana Ratiaria (107 AD). In the 2nd and 3rd centuries, it prospered as a trade center. With the definitive abandonment of Dacia Traiana in 271, old castra were reopened. By 285, Ratiaria served as the capital of Dacia Ripensis, hosting the military governor and the Roman legion XIII Gemina. It later became an important Christian center in the 4th century, with recorded bishops and theologians. The city faced sackings by the Huns in 440-441 and the Avars in AD 586. Archaeological excavations started in 1958, revealing its historical significance.
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.