Four-centred arch

[a] The four-centered arch is widely used in Islamic architecture, originally employed by the Abbasids and later by the Fatimids and by Persianate cultures.

The earliest examples of a four-centered arch were introduced at Samarra, a purpose-built capital built by the Abbasids in the 9th century.

[3][4]: 25, 250–251  Later, the four-centered arch appeared commonly in the architecture of the Ghurid Empire, which ruled over large parts of Iran, Central Asia, and the northern Indian Subcontinent in the 12th to 13th centuries.

[3] Blind keel arch niches appeared frequently as a motif of decorated façades in late Fatimid, Ayyubid, and early Mamluk architecture in Cairo.

However, numerous simpler buildings, especially churches built during the wool boom in East Anglia and the Cotswolds, also demonstrate the style.

When employed to frame a large church window, it lends itself to very wide spaces, decoratively filled with many narrow vertical mullions and horizontal transoms.