At its core, this abbey, situated in the middle of the Premonstratensian monastery at Strahov, is a Romanesque basilica with a Gothic transept and two Renaissance towers (with Baroque modifications). The church received its current Baroque appearance between 1742 and 1758. The side walls are decorated with frescoes in cartouches depicting scenes from the life of St Norbert, the founder of the order. A Gregorian choir sings during masses.
The Church of the Assumption of Virgin Mary is in its core a three-aisle Romanic basilica with a Gothic transept, prolonged in 1627, and with a Renaissance chancel. The church was built in the 3rd quarter of the 12th century. It was rebuilt in a Gothic style in the years 1258 – 1263, and this appearance outlived centuries. Historical research in the 1950s did not find proofs of the devastating fire in the 13th century, or of the destruction of the church by the Hussites. In 1601 – 1605, the era of abbot Lohel, there was a Renaissance reconstruction probably drafted by G. Bossi de Campione. It was damaged during the shelling and bombing of Prague in 1742, and subsequently, late-Baroque modifications were made on the church’s front (T. Haffeanecker, A. Lurago, sculptural decorations by Jan Antonín Quittainer), as well as in the interior: frescoes from the life of St. Norbert and scenes from the life of Virgin Mary by a Silesian painter Vilém Neuenherz (1743). Stucco decoration by Jan Palliardi, the main alter and 10 side altars by the renowned Prague stonemason Josef Lauermann (1769). The statues on the main altar were made by Ignác Platzer, the statues on the side altars by J. A. Quittainer. Paintings on the altars were mostly made by M. Leopold Willmann, F. Xaver Balko and Siard Nosecký.
From the very beginning, chapels were being added to the church. In the middle of the aisle, there is the Chapel of Virgin Mary of Passau (in place of a Gothic Chapel of St. Angels from the 14th century). It was built by Albrecht of Valdštejn for the imperial general Pappenheim and Albrecht’s nephew Berthold, who died in the Battle of Lützen. There is a copy of the painting of Virgin Mary of Passau on the altar, and on the ceiling, there is a fresco depicting the Battle of Lützen by Siard Nosecký. On the opposite side of the church, there is a larger Chapel of St. Voršila, which was Gothic, originally. There is an altar of St. Voršila and an altar of St. Norbert, the founder of the Premonstrate Order and the land patron, the remains of who were brought to Strahov from a Magdeburg Premonstrate Monastery in 1627 and are buried in this chapel. The church’s co-founder, Vladislav II, was also buried in the church in 1174, and before him his wife Gertruda, just like the second co-founder Jindřich Zdík (died in 1150). However, their graves were not found during archaeological research.
Famous organists Jan Křtitel Kuchař and Robert Führer played in the church. In 1787, W. A. Mozart improvised on the local organ. The original organ was replaced after 1900.
Pope John Paul II bestowed the abbot’s temple of the Assumption of Virgin Mary with a title Basilica minor (smaller basilica). The promotion was celebrated on the 1st and the 2nd February 1992.
Source: https://www.prague.eu/en/object/places/429/basilica-of-the-assumption-of-the-virgin-mary-at-strahov-bazilika-nanebevzeti-panny-marie-na-strahove