Clementinum

The Clementinum (Klementinum) is the second largest architectural complex in Prague after Prague Castle, covering over 20,000 m² in the Old Town just steps from Charles Bridge. Built by the Jesuits between 1556 and 1726 on the site of a Dominican monastery, it now houses the National Library of the Czech Republic — one of the oldest and largest libraries in Europe with over six million documents. The complex is visited for three exceptional spaces: the Baroque Library Hall (1722), a breathtaking two-storey room with ceiling frescoes by Jan Hiebl, ornate globes, and 20,000 historical volumes; the Meridian Hall, used to determine noon by a shaft of sunlight until the 20th century; and the 68-metre Astronomical Tower, where continuous meteorological measurements have been recorded since 1775 — the longest unbroken climate record in Central Europe. The Mirror Chapel, decorated with mirrors and 18th-century frescoes, serves as a celebrated venue for classical concerts and was famously played on by Mozart during his Prague visits.