Lady chapel

A Lady chapel or lady chapel is a traditional British term for a chapel dedicated to "Our Lady", the Blessed Virgin Mary, particularly those inside a cathedral or other large church. The chapels are also known as a Mary chapel or a Marian chapel, and they were traditionally the largest side chapel of a cathedral, placed eastward from the high altar and forming a projection from the main building as in Winchester Cathedral. Most Roman Catholic and many Anglican cathedrals still have such chapels, while mid-sized churches have smaller side-altars dedicated to the Virgin.

In the 12th-century legends surrounding King Lucius of Britain, the apostles Fagan and Duvian were said to have erected the Lady Chapel at Glastonbury as the oldest church in Britain; the accounts are now held to have been pious forgeries. The earliest English lady chapel of certain historicity was that in the Saxon cathedral of Canterbury; this was transferred in the rebuilding by Archbishop Lanfranc to the west end of the nave, and again shifted in 1450 to the chapel on the east side of the north transept. The lady chapel of Ely Cathedral is a distinct building attached to the north transept which was built before 1016. At Rochester the current lady chapel is west of the south transept (which was the original lady chapel, and to which the current chapel was an extension).

...
Wikipedia