A tower block, residential towers, apartment tower, office tower, apartment block, or block of flats, is a tall building or structure used as a residential and/or office building. In some areas they may be referred to as "MDU" standing for "Multi Dwelling Unit".
High-rise buildings became possible with the invention of the elevator (lift) and cheaper, more abundant building materials. The materials used for the structural system of high-rise buildings are reinforced concrete and steel. Most North American style skyscrapers have a steel frame, while residential blocks are usually constructed of concrete. There is no clear definition of any difference between a tower block and a skyscraper, although a building with fifty or more storeys is generally considered a skyscraper.
High-rise structures pose particular design challenges for structural and geotechnical engineers, particularly if situated in a seismically active region or if the underlying soils have geotechnical risk factors such as high compressibility or bay mud. They also pose serious challenges to firefighters during emergencies in high-rise structures. New and old building design, building systems like the building standpipe system, HVAC systems (heating, ventilation and air conditioning), fire sprinkler system and other things like stairwell and elevator evacuations pose significant problems.
Śródmieście [ɕrudˈmʲeɕt͡ɕe] (meaning "city centre", "downtown") is the central borough (dzielnica) of the city of Warsaw. The best known neighborhoods in the borough are the Old Town (Stare Miasto) and New Town (Nowe Miasto).
The area is home to the most important national and municipal institutions, many businesses, higher education establishments (e.g. Warsaw University, Warsaw University of Technology and Medical Academy) and theatres. It is also home to most of the tourist attractions in Warsaw, including the tallest building in Warsaw (234 m), the narrowest street (5.3 m), the oldest university (est. 1809), the oldest public park (opened 1772), the oldest secular monument (1644) and the oldest historical building (13th century).
The name is also colloquially used for Warszawa Śródmieście railway station.