Most downtown buildings from this era are four-story mix-use (residential and commercial) buildings with ceilings, allowing for the construction of mezzanines. Despite their less-than-perfect conditions, the buildings remain highly sought after and most expensive in the city's property market. In 1996, the Yangon City Development Committee created a Yangon City Heritage List of old buildings and structures in the city that cannot be modified or torn down without approval. In 2012, the city of Yangon imposed a 50-year moratorium on demolition of buildings older than 50 years. The Yangon Heritage Trust, an NGO started by Thant Myint-U, aims to create heritage areas in Downtown, and attract investors to renovate buildings for commercial use. A latter-day hallmark of Yangon is the eight-story apartment building. (In Yangon parlance, a building with no elevators (lifts) is called an apartment building and one with elevators is called a condominium. Condos which have to invest in a local power generator to ensure 24-hour electricity for the elevators are beyond the reach of most Yangonites.) Found throughout the city in various forms, eight-story apartment buildings provide relatively inexpensive housing for many Yangonites. The apartments are usually eight stories high (including the ground floor) mainly because city regulations, until February 2008, required that all buildings higher than or eight stories to install lifts. The current code calls for elevators in buildings higher than or six stories, likely ushering in the era of the six-story apartment building. Although most apartment buildings were built only within the last 20 years, they look much older and rundown due to shoddy construction and lack of proper maintenance. Unlike other major Asian cities, Yangon does not have any skyscrapers. Aside from a few high-rise hotels and office towers, most high-rise buildings (usually 10 stories and up) are "condos" scattered across prosperous neighborhoods north of downtown such as Bahan, Dagon, Kamayut and Mayangon. Older satellite towns such as Thaketa, North Okkalapa, and South Okkalapa are lined mostly with one to two-story detached houses with access to the city's electricity grid. Newer satellite towns such as North Dagon and South Dagon are in a grid layout. The satellite towns—old or new—receive little or no municipal services. Downtown Yangon's road layout follows a grid pattern, based on four types of roads:  The east-west grid of central was laid out by British military engineers Fraser and Montgomerie after the Second Anglo-Burmese War.