The grand arch is a monument to Queen Victoria. Its construction was finished in 1912 and for most of its existence it was owned by the Admiralty and served as an office building. However, a significant part of it was sold to the private owners in 2012 to be transformed into a luxurious hotel.
It becomes an important place during various ceremonies. When there is a royal ceremony such as wedding, funeral or coronation, the procession passes under the Arch.
From the Arch, you can stroll down the Mall, the boulevard that will take you straight to the Buckingham Palace.
Wikipedia https://en.wikipedia.org/wiki/Admiralty_Arch
Official site http://www.admiraltyarch.co.uk/
Email info@admiralityarch.co.uk
Address The Mall, London SW1A 2WH, UK
Coordinates 51°30'24.167" N -0°7'42.861" E