St. John's Co-Cathedral is a Roman Catholic church located in Valletta, Malta. Built in the 16th century, it served as the conventual church of the Knights of St. John. The cathedral is renowned for its stunning Baroque architecture and richly decorated interior, featuring intricate carvings and vibrant frescoes. Inside, visitors can admire the famous paintings by Caravaggio, including "The Beheading of Saint John the Baptist." The cathedral also houses the tombs of several Grand Masters of the Order of St. John, making it a significant historical and cultural site in Malta.