The largest section open to the public today consists of the casemates, underground spaces built from the late 17th to the early 19th century, originally serving as protected storerooms and shelters for the garrison. Some of the passages are hewn directly into the rock, while others are lined with thick stone vaulting. The total length of accessible corridors exceeds 300 metres, and at various points they open into chambers with views over the Vltava or into the interior of a bastion. The spaces have a character all their own, shaped by the combination of military austerity and dramatic concealment: in one moment you are dozens of metres below the park, beneath strolling visitors and the towers of the basilica, in complete silence.
Guided tours of the Vyšehrad underground are organised by the administration of the national cultural monument and are available in both Czech and English. Entry is possible only with a guide and advance booking is required. Combining a visit to the underground with a tour of the grounds, the cemetery and the basilica makes Vyšehrad one of the richest historical sites in Prague that can be explored within a single afternoon.