The Church of St. Adalbert is one of the oldest stone churches in Poland. The Church was built in the 11th century and named after the martyred missionary Saint Adalbert whose body was bought back for its weight in gold from the pagan Prussia and placed in Gniezno Cathedral by Boleslaus I of Poland. The interior of the church is cramped, relative to its larger exterior. The floor level is situated under the present level of the Square, which reflects the overlaying of the subsequent surfaces of the plaza with pavement originally adjusted to the two already existing churches (St. Wojciech/Adalbert and St. Mary's Basilica). The church was partially reconstructed in the Baroque style between 1611-1618.
According to the Archeological Museum of Kraków, the oldest relics reveal a wooden structure built at the end of the 10th century and followed by an original stone church constructed in the 11th century, as seen in the lower parts of the walls. These walls became a foundation for a new church built around the turn of the 11th and 12th centuries from smaller rectangular stones. Since the level of the plaza, overlaid with new pavement, rose between 2 to 2.6 meters, the walls of the church were raised up in the 17th century and then covered with stucco. The new entrance was built from the west side and the church was topped with the new Baroque dome. The restoration of the church conducted in the 19th century led to the discovery of its Romanesque past.
At present, the walls of the church are unearthed to show their lowest level. On the south side there's a Romanesque portal and corresponding stone step. The crypt of the church has been adapted by the Archeological Museum as a small Museum of the History of the Market Square showing a permanent exhibit of 'The History of the Kraków Market.'
References:The Clementinum is a historic complex of buildings in Prague. Until recently the complex hosted the National, University and Technical libraries, the City Library also being located nearby on Mariánské Náměstí. The Technical library and the Municipal library have moved to the Prague National Technical Library at Technická 6 since 2009. It is currently in use as the National Library of the Czech Republic.
Its history dates from the existence of a chapel dedicated to Saint Clement in the 11th century. A Dominican monastery was founded in the medieval period, which was transformed in 1556 to a Jesuit college. In 1622 the Jesuits transferred the library of Charles University to the Klementinum, and the college was merged with the University in 1654. The Jesuits remained until 1773, when the Klementinum was established as an observatory, library, and university by the Empress Maria Theresa of Austria.