St. John's Chapel is located in the Tower of London

Tower of London

Her Majesty's Royal Palace and Fortress, more commonly known as the Tower of London, is a historic castle on the north bank of the River Thames in central London, England. It lies within the London Borough of Tower Hamlets, separated from the eastern edge of the City of London by the open space...

. Dating from 1080, this complete 11th-century church is the oldest church in London

London

London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

.

A Romanesque

Romanesque architecture

Romanesque architecture is an architectural style of Medieval Europe characterised by semi-circular arches. There is no consensus for the beginning date of the Romanesque architecture, with proposals ranging from the 6th to the 10th century. It developed in the 12th century into the Gothic style,...

 chapel, St. John's is on the second floor of the White Tower

White Tower (Tower of London)

The White Tower is a central tower, the old keep, at the Tower of London.-History:The castle which later became known as the Tower of London was built by William the Conqueror in 1066. It began as a timber fortification enclosed by a palisade. In the next decade work began on the White Tower, the...

, which was built in 1077–97 as a keep

Keep

A keep is a type of fortified tower built within castles during the Middle Ages by European nobility. Scholars have debated the scope of the word keep, but usually consider it to refer to large towers in castles that were fortified residences, used as a refuge of last resort should the rest of the...

 or citadel, the oldest part of William the Conqueror's powerful fortress. It was constructed from stone imported from France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, and has a tunnel-vaulted nave

Nave

In Romanesque and Gothic Christian abbey, cathedral basilica and church architecture, the nave is the central approach to the high altar, the main body of the church. "Nave" was probably suggested by the keel shape of its vaulting...

 with an east apse

Apse

In architecture, the apse is a semicircular recess covered with a hemispherical vault or semi-dome...

 and groin-vaulted aisles, and the gallery above curves around the apse. Thick, round piers support unmoulded arches, notable for their simplicity, with simple carvings of scallop and leaf designs providing the only decoration.

The chapel has survived complete from the early Norman

Norman conquest of England

The Norman conquest of England began on 28 September 1066 with the invasion of England by William, Duke of Normandy. William became known as William the Conqueror after his victory at the Battle of Hastings on 14 October 1066, defeating King Harold II of England...

 period, whereas other Norman churches in England date from the mid-12th century. Because St Peter ad Vincula is the parish church of the Tower of London, St. John's Chapel is often overlooked.

Services are held in the chapel periodically during the year.