Karlštejn Castle stands on a wooded limestone hill about thirty kilometres southwest of Prague, a stepped procession of walls and towers that Charles IV — King of Bohemia and Holy Roman Emperor — founded in 1348. He built it for a singular purpose: to house and protect the imperial regalia, the Bohemian crown jewels and a great collection of holy relics. It remains one of the most famous and most visited castles in the Czech Republic, and one of the easiest heritage day trips from the capital.
The castle's interiors are seen only on guided tours, and the two English-language tours reach very different heights. Tour I leads through the Imperial Palace — the private and audience rooms of Charles IV in the lower castle. Tour II climbs to the summit of the Great Tower and the castle's crowning glory: the Chapel of the Holy Cross, its walls encrusted with more than two thousand polished semi-precious stones and lined with 129 medieval panel paintings by Master Theodoric, once the strong-room for the Empire's crown jewels themselves.
That upper tour is where a booking service earns its place. Tour II is reservation-only, capped at sixteen people per departure and offered only from spring to autumn, so international visitors who simply turn up are routinely turned away. We watch the operator's live availability, secure an English departure on the date you want, explain which tour reaches the Chapel, and make sure a sold-out day doesn't cost you one of Bohemia's greatest sights.