These rectilinear forms were complemented from the mid-19th century with more serpentine forms, starting with Cockburn Street, laid out by Peddie and Kinnear in 1856, which specifically improved access between the Royal Mile and the newly rebuilt Waverley Station. The Edinburgh City Improvement Act of 1866 further added to the north south routes. This was devised by the architects David Cousin and John Lessels. It had quite radical effects:   In addition to the Royal Mile, the Old Town may be divided into various areas, namely from west to east:  Due to the space restrictions imposed by the narrowness of the "tail", and the advantages of living within the defensive wall, the Old Town became home to some of the world's earliest "high rise" residential buildings. Multi-storey dwellings became the norm from the 16th century onwards. Many of these buildings were destroyed in the Great Fire of Edinburgh in 1824; the rebuilding of these on the original foundations led to changes in the ground level and the creation of numerous passages and vaults under the Old Town. The construction of new streets including North Bridge and South Bridge in the 18th century also created underground spaces, such as the Edinburgh Vaults below the latter. Traditionally buildings were less dense in the eastern, Canongate, section. This area underwent major slum clearance and reconstruction in the 1950s, thereafter becoming an area largely of Council housing. From 1990 to 2010, major new housing schemes appeared throughout the Canongate. These were built to a much higher scale than the older buildings and have greatly increased the population of the area. In 1824 a major fire, the Great Fire of Edinburgh, destroyed most of the buildings on the south side of the High Street section between St. Giles Cathedral and the Tron Kirk. During the Edinburgh International Festival the High Street and Hunter Square become gathering points where performers in the Fringe advertise their shows, often through street performances. On 7 December 2002, the Cowgate fire destroyed a small but dense group of old buildings on the Cowgate and South Bridge. It destroyed the famous comedy club, The Gilded Balloon, and much of the Informatics Department of the University of Edinburgh, including the comprehensive artificial intelligence library. The site was redeveloped 2013-2014 with a single new building, largely in hotel use. In the 1990s the Old Town Renewal Trust in conjunction with the City of Edinburgh developed an action plan for renewal   An area directly to the north of the Canongate has been earmarked for a large redevelopment project named Caltongate.