Rebuilt by the Crusaders as an octagonal chapel, it was transformed into a mosque after 1187. A square on the floor is said to mark the spot at which Jesus ascended to heaven. Outside, note the capitals of the columns. Ask to see the nearby tomb of Pelagia, an early Christian saint who disguised herself as a monk for many years until her secret was revealed when she died. To enter, ring the bell by the mosque; there is a small fee. A small gift stand sells postcards and other souvenirs.