On the north side of the square are three 18th-century historic buildings, which were the city's heart in the colonial era. The center of the three is St. Louis Cathedral. The cathedral was designated as a minor Basilica by Pope Paul VI. To its left is the "Cabildo", the old city hall, now a museum, where the final version of the Louisiana Purchase was signed. To the cathedral's right is the "Presbytère", built to match the Cabildo. The Presbytère was initially planned for housing the city's Roman Catholic priests and other church officials. At the start of the 19th century, it was adapted as a courthouse, and in the 20th century it became a museum.