This imposing white arch was originally used to serve as an entry to the Buckingham Palace, the arch was moved here in 1851. Only members of the Royal Family can pass under it during various ceremonies.
The arch was designed by a well-known British architect John Nash, who also worked on the Buckingham Palace and on the Royal Pavilion in Brighton. Inspired by Rome's Arch of Constantine, this piece of architecture is an eye-candy of the park.
If you plan on using public transport to get here, the Marble Arch is right next to metro and bus station with the same name.
Wikipedia https://en.wikipedia.org/wiki/Marble_Arch
Address 1-3 Marble Arch, Paddington W1H 7EL, United Kingdom
Coordinates 51°30'47.433" N -0°9'32.172" E