The Church of St. Haštal (Castulus), founded in the late 12th century, is the only church dedicated to this saint in the country. Since its founding, it also had a school and a rectory with a garden, surrounded by massive walls – today the building is used by various religious groups and organizations. There used to be a cemetery around the church, its presence marked by a cross in the mosaic pavement; even today the former ossuary with a painted tombstone on the wall still stands. At the corner of Řásnovka Street stands an unusual rounded corner building – the former hospital of the Knights of the Cross with the Red Star, the only originally Bohemian order and the only men’s order founded by a woman, princess Agnes of Bohemia. The original building was demolished in 1965 and replaced with a new building that stands on the original hospital foundations and copies its ground plan.
Source: https://www.prague.eu/en/object/places/3008/hastalske-namesti-hastal-square