The Pisa Baptistery, also known as the Baptistery of St. John (Battistero di San Giovanni) is a Roman Catholic ecclesiastical building in Pisa, Italy. Its construction began in 1152, making it the second oldest building on Pisa's Piazza dei Miracoli, between the cathedral and the bell tower, which is now the famous Leaning Tower of Pisa. The Baptistery was designed by Diotisalvi, whose signature can be seen on two columns inside the building, dated 1153.