Grosvenor Square is a large garden square in the Mayfair district of London. It is the centrepiece of the Mayfair property of the Duke of Westminster, and takes its name from the duke's surname "Grosvenor". It was developed for fashionable residences in the 18th century. In the 20th it had an American and Canadian diplomatic presence, and currently is mixed use, commercial. History Sir Richard Grosvenor obtained a licence to develop Grosvenor Square and the surrounding streets in 1710, and development took place between 1725 and 1731. The land was sold in individual plots, with 30 different builders or partnerships taking a lease; about half of these had become bankrupt by 1738. Grosvenor Square was one of the three or four most fashionable residential addresses in London from its construction until the Second World War, with numerous leading members of the aristocracy in residence. The early houses were generally of five or seven bays, with basement, three main stories and an attic. Some attempt was made to produce impressive groupings of houses, and Colen Campbell produced a design for a palatial east side to the square featuring thirty Corinthian columns but this was not carried out and in the end most of the houses were built to individual designs. There were mews behind all four sides. Many of the houses were rebuilt later in the 18th century or during the 19th century, generally acquiring an extra storey when this happened. Number 23 (later 26) was rebuilt in 1773–74 for the 11th Earl of Derby by Robert Adam, and is regarded as one of the architect's finest works and as a seminal example of how grandeur of effect and sophisticated planning might be achieved on a confined site. It was demolished and rebuilt again in the 1860s. Nearly all of the older houses were demolished during the 20th century and replaced with blocks of flats in a neo-Georgian style, hotels and embassies. The garden Providing almost 2.5 hectares of open garden, Grosvenor Square is the second-largest garden square in central London after Russell Square at 2.5 hectares. While Lincoln's Inn Fields at 4.5 hectares is a larger space, it is categorised as an Inn of Court, not a garden square. Grosvenor Square was originally laid out by gardener John Alston in the 1720s; his 'wilderness worke' design was a celebration of the countryside in the city. However, the gardens have been