The Klementinum's baroque library hall is the room people come for: two storeys of gilded cases under a ceiling Jan Hiebel painted as a temple of wisdom, with old globes standing down the middle. You see it from the doorway and go no further, because the floor and the air inside are protected. The rest of the complex is a small town of courtyards — a church, a theatre, an observatory tower — built up by Jesuits who arrived in 1556 and kept buying the houses around them.
The order was dissolved in 1773 and the state took the buildings. The national library has worked in them ever since, so the courtyards are a place of work rather than a museum, crossed by readers and students rather than tour groups. Above the roofs stands the astronomical tower of 1722, and in a hall beneath it a meridian line still marks true noon. The astronomer Antonín Strnad began the daily weather readings here, and they have never stopped.