The site is enclosed by a boundary wall with a monument to John Playfair, president of the Edinburgh Astronomical Institution, in the southeast corner (part of the complex designed by William Playfair, 1818). The oldest part is the Gothic Tower (1775-1777) in the southwest corner, facing Princes Street and Edinburgh Castle. It is also known as Observatory House, the Old Observatory, or after its designer, James Craig House. The central building with the appearance of a Greek temple is the Playfair Building (1818), named after the building's designer William Henry Playfair. This houses the 6-inch (15 cm) refractor in its dome and the 6.4-inch (16 cm) transit telescope in its eastern wing. The largest dome of the site is the City Dome (1898) in the northeast corner. During the early 20th century this contained a 22-inch (56 cm) refractor.