of streets composed entirely of stairs, and many other steep streets with stairs for sidewalks. Many provide vistas of the Pittsburgh area while attracting hikers and fitness walkers. Bike and walking trails have been built to border many of the city's rivers and hollows. The Great Allegheny Passage and Chesapeake and Ohio Canal Towpath connect the city directly to downtown Washington, D.C. (some away) with a continuous bike/running trail. Cityscape Areas The city consists of the Downtown area, called the Golden Triangle, and four main areas surrounding it. These surrounding areas are subdivided into distinct neighborhoods (Pittsburgh has 90 neighborhoods). Relative to downtown, these areas are known as the Central, North Side/North Hills, South Side/South Hills, East End, and West End. Golden Triangle Downtown Pittsburgh has 30 skyscrapers, nine of which top . The U.S. Steel Tower is the tallest, at . The Cultural District consists of a 14-block area of downtown along the Allegheny River. This district contains many theaters and arts venues and is home to a growing residential segment. Most significantly, the Pittsburgh Cultural Trust is embarking on RiverParc, a four-block mixed-use "green" community, featuring 700 residential units and multiple towers of between 20 and 30 stories. The Firstside portion of Downtown borders the Monongahela River, the historic Mon Wharf and hosts the distinctive PPG Place Gothic-style glass skyscraper complex. New condo towers have been constructed and historic office towers are converted to residential use, increasing 24-hour residents. Downtown is served by the Port Authority's light rail system and multiple bridges leading north and south. It is also home to Point Park University and Duquesne University which borders Uptown. North Side The North Side is home to various neighborhoods in transition. What is known today as Pittsburgh's North Side was once known as Allegheny City, and operated as a city independently of Pittsburgh until it was merged with Pittsburgh in 1907 under great protest from its citizens. The North Side is primarily composed of residential neighborhoods and is noteworthy for its well-constructed and architecturally interesting homes. Many buildings date from the 19th century and are constructed of brick or stone and adorned with decorative woodwork, ceramic tile, slate roofs and stained glass. The North Side is also home to attractions such as Acrisure Stadium, PNC Park, Carnegie Science Center, National Aviary, Andy Warhol Museum, Mattress Factory art museum, Children's Museum of Pittsburgh, Randyland, Penn Brewery, Allegheny Observatory,