From the Wikipedia page :
The Monument to the Great Fire of London, more commonly known simply as the Monument, is a stone Roman Doric column in the City of London, near the northern end of London Bridge, which commemorates the Great Fire of London.
It stands at the junction of Monument Street and Fish Street Hill, 202 ft (62 m) tall and 202 ft (62 m) from the place where the Great Fire started on 2 September 1666. Another monument, the Golden Boy of Pye Corner, marks the point near Smithfield where the fire stopped. Constructed between 1671 and 1677, it is the tallest isolated stone column in the world and was built on the site of St. Margaret's, Fish Street, the first church to be burnt down by the Great Fire.
The official website is