Members of Journeymen Jesus order – Jesuits came to Prague in 1556 led by, later on canonized, Peter Canisi. They founded several centres in Prague historical towns, from which Klementinum in Prague Old Town was counted as the most significant. With support of the emperor, aristocracy, commons and also thanks to many gifts and entitlements Jesuits gradually through out the period lasted over 200 years built a large complex essentially of the same resemblance as we know it today. Klementinum became a centre of not only catholic religion but also a centre of education.

Dominant feature of Klementinum is Astronomical Tower, earlier known also as Mathematical Tower. The tower was build by Jesuits already in 1722. Its original state was not unfortunately preserved. Jesuits decided to rebuild the tower approximately in mid of 18th century. According to available data the reconstruction took too long, probably from 1749 until 1777, whereas the top of the tower was contractually reached already in 1751. The Jesuit Order was suppressed in line with Bull on 21 July 1773.

Mathematician, physician and astronomer, Josef Stepling (1716-1778) had imperishable merit for the tower reconstruction and in particular for equipping it with astronomical instruments. That is why there is a monument in his honour standing in the courtyard of Klementinum.

In 1891-1911 so called Prague midday use to be signalled by cannonade. With help of the unique crexicular solar clock and the time-measuring instruments the man in tower found the actual time and at he walked onto the gallery at12 o’clock and sent a signal with flag. Then the cannoneers, prepared on Mariánské walls, fired out.

The tower of Klementinum is 52 m tall and the statue of Atlas bearing the Earth, with a symbol of Goods eye, is on its top. The statue was relocated from the original tower and comes from the plant of famous Matyas Bernard Braun.