A cross-in-square or crossed-dome plan was the dominant architectural form of middle- and late-period Byzantine churches. It featured a square centre with an internal structure shaped like a cross, topped by a dome.
The first cross-in-square churches were probably built in the late 8th century, and the form has remained in use throughout the Orthodox world unto the present day. In the West, Donato Bramante's first design (1506) for St. Peter's Basilica was a centrally planned cross-in-square under a dome and four subsidiary domes.
In German, such a church is a Kreuzkuppelkirche, or 'cross-dome church'. In French, it is an église à croix inscrite, 'church with an inscribed cross'.