The Klementinum Baroque Library — What You'll Actually See
A close look at the Klementinum's 1722 Baroque Library Hall, the Astronomical Tower views, and the Mirror Chapel — the three rooms every guided tour covers.
The Klementinum is the largest building complex in Prague's Old Town after Prague Castle — a 17th-century Jesuit college turned into the Czech National Library. Most visitors come for one specific room: the Baroque Library Hall of 1722, regularly listed among the world's most beautiful libraries. The Klementinum is accessible only by guided tour, and the standard tour covers three rooms — the library, the Astronomical Tower and the Mirror Chapel. Here's what you'll actually see in each.
The Baroque Library Hall (1722)
The Baroque Library Hall is the centrepiece. Completed in 1722, the room runs about 50 metres long with a vaulted ceiling frescoed by Jan Hiebl depicting the Temple of Wisdom — the Greek and Roman scholars of antiquity flanked by the Jesuit reformers. The two-storey wooden shelves still hold the original Jesuit theological collection, around 20,000 volumes bound in white parchment with red labels. Visitors view the hall from a roped-off threshold; entry into the room itself is restricted to preserve the climate and books. Photography rules are strict — usually no photos at all, sometimes mobile-only with no flash. Confirm the current photography policy with the operator before your tour.
Two details to look for. The wooden globes mid-room: four large celestial and terrestrial globes from the 17th century, made by the Jesuit cartographers. The astronomical instruments at the back: pendulums and quadrants used when the Klementinum was central Europe's leading observatory. The library is in active conservation; some volumes are off-shelf at any given time for restoration. The guided tour pauses at the threshold for 8–10 minutes — the only stop on the standard tour where you stand still long enough to take the room in properly.
The Astronomical Tower (172 steps)
From the library, the tour climbs the Astronomical Tower — 172 steps, no lift. The tower was built in 1722 as an observatory, and Czech daily weather measurements have been recorded here continuously since 1775, the longest continuous weather record in central Europe. The climb is steep but manageable for most visitors; the staircase widens in the upper section. The viewing platform at the top gives a 360° panorama of Prague's red roofs, the Old Town Square's Týn Cathedral spires, the river bend and Prague Castle on the opposite ridge.
Inside the tower, the tour pauses at the meridian room — the original brass meridian line embedded in the floor, used for the noon time-signal that defined Prague time until the 1920s. A man would stand at the small upper window at solar noon and signal to the rooftops below. The view from the platform is comparable to the Old Town Hall Tower (Astronomical Clock) but with a more dramatic angle on the castle and less crowded. Most visitors rate the tower as the highlight of the whole tour.
The Mirror Chapel
The third tour stop is the Mirror Chapel of 1724, named for the gilded mirrors set into the ceiling and walls. The chapel was originally the Marian congregation hall of the Jesuit college; it functions today primarily as a concert venue, and visiting the chapel as part of the tour gives you a 5-minute look at the architecture. The acoustics are exceptional — Mozart performed here as a guest of the Jesuit fathers in 1787, and the chapel still hosts daily classical concerts in the evening (separate ticket, typically Vivaldi, Mozart and Bach programmes).
Tour-time visitors see the chapel quietly and briefly. If you want a longer experience and the acoustics in use, book one of the evening concerts (separate from the daytime guided tour). The chapel's gilded mirror panels reflect light during concerts in a way photographs cannot capture; the evening concert is the best way to experience the room as it was designed to be used.
Tour logistics — what to expect on the day
The standard guided tour runs about 50 minutes and is held in either Czech or English, with English tours hourly during peak season. The tour is the only way to see the library and the Astronomical Tower — there is no self-guided option. Groups are capped at around 20 people. Tours start from the Klementinum visitor centre on Křižovnické náměstí, across from Charles Bridge.
The library is the room everyone comes for, but the Astronomical Tower view is what most visitors remember. Plan to arrive 10 minutes before your timed tour start; latecomers are not admitted because the tour moves through one-direction doors. The Klementinum is a working library — silence is expected at the library threshold, voices are fine in the corridors and tower. The full visit including tower climb and a moment in the courtyard takes about 90 minutes door-to-door.
Frequently asked
Can I visit the Klementinum on my own without a guided tour?
No — the Baroque Library Hall and Astronomical Tower are only accessible by guided tour. The Klementinum is a working National Library and the inner rooms are not self-guided. The courtyard is freely accessible; the library and tower require a paid timed-entry tour.
How long is the Klementinum guided tour?
About 50 minutes, covering three rooms: the Baroque Library Hall (8–10 minutes at the threshold), the Astronomical Tower (15 minutes including the 172-step climb), and the Mirror Chapel (5 minutes). Total visit door-to-door including arrival and courtyard time is around 90 minutes.
Can I take photos inside the Klementinum library?
Photography rules are restrictive. Typically no photography is allowed inside the Baroque Library Hall; sometimes mobile-only with no flash. The Astronomical Tower and Mirror Chapel permit photography. Confirm the current photography rules with the operator before your tour.
Are tours offered in English?
Yes — English-language tours run hourly during peak season. Czech tours run more frequently. Tours in other languages (German, Spanish, Italian) are scheduled less frequently and book out faster. Check the schedule for the day of your visit.
Is the Astronomical Tower accessible for visitors with mobility issues?
No — the tower is reached by 172 steps with no lift. The staircase is steep in the lower section, wider in the upper section. The Baroque Library Hall threshold is accessible with one small step from the corridor. The Mirror Chapel is step-free. Visitors who cannot climb the tower can still take the library + chapel parts of the tour.
Is the Klementinum the same as the Old Town Hall with the Astronomical Clock?
No — they are two different buildings. The famous Prague Astronomical Clock with the hourly Apostles parade is on the Old Town Hall facade. The Klementinum has the Astronomical Tower (an observatory tower from 1722) and is a former Jesuit college and library, located on the opposite side of the Old Town Square near Charles Bridge.