Located in the ground floor of Westminster’s three-storied Jewel Tower is a fine 14th-century ribbed vault, described as an “architectural masterpiece”.

The room is believed to have been constructed, along with the rest of the building, in the 1360s to the designs of master mason Henry de Yevele.

Located in the south-west corner of Old Palace Yard, the tower was originally used as a personal treasure-house for King Edward III and was known as the King’s Privy Wardrobe. Later it was used to house government documents and in 1869 became the Weights and Measures Office.

It is one of few surviving buildings from the medieval Palace of Westminster (the rest having been destroyed in the fire of 1834).

The vaulted chamber incorporates tiercerons – ribs set between the transverse and diagonal ribs to form simple fans and also features a series of sculpted bosses.

Made in Reigate stone, these depict human and mythical animal heads, as well as intertwined pairs of eagles and swans and plant designs. It is believed the bosses were once whitened.

The west wall of the chamber features the remains of a fireplace while the main window reveal is medieval (although the window itself dates from the 18th century).

The property, which is under the care of English Heritage, is not to be confused with the Jewel House at the Tower of London.

WHERE: The Jewel Tower, Abingdon Street, Westminster, (nearest Tube stations are Westminster and St James’s Park); WHEN: 10am to 4pm on weekends; COST: £6 adults/£3.60 children (aged five to 17 years)/£5.30 concession; family tickets available; WEBSITE: www.english-heritage.org.uk/visit/places/jewel-tower/