Marble Arch

Marble Arch is a 19th-century white marble-faced triumphal arch in London, England. The structure was designed by John Nash in 1827 to be the state entrance to the cour d'honneur of Buckingham Palace; it stood near the site of what is today the three-bayed, central projection of the palace containing the well-known balcony. In 1851, on the initiative of architect and urban planner Decimus Burton, a one-time pupil of John Nash, it was relocated to its current site. Following the widening of Park Lane in the early 1960s, the site became a large traffic island at the junction of Oxford Street, Park Lane and Edgware Road, isolating the arch. Admiralty Arch, Holyhead in Wales is a similar arch, also cut off from public access, at the other end of the A5.

Only members of the Royal Family and the King's Troop, Royal Horse Artillery are said to be permitted to pass through the arch; this happens in ceremonial processions.

Wikipedia