Pittsburgh ( ) is the second largest city in the Commonwealth of Pennsylvania with a population of 334,563 and the 22nd largest metropolitan area in the United States with a population of 2,658,695 . It is the county seat of Allegheny County, Pennsylvania. Built on land surrounding the confluence of the Allegheny and Monongahela rivers, where they merge to form the Ohio river, Pittsburgh features a skyline of 151 high-rise buildings, blank">"High-rise Buildings of Pittsburgh" 446 bridges, Pitt Chronicle: "Venice, Schmenice" two inclined railways and a pre-revolutionary fortification. Residents of the city are called Pittsburghers. The _downtown area is located on the triangular parcel at the confluence of the rivers. Pittsburgh is noted for bridges of all types throughout the city and is commonly known as the "The City of Bridges" or "The Bridge Capital" of the U.S.

Though Pittsburgh's economy was traditionally fueled by heavy manufacturing to the detriment of local air and water quality, today it is largely based on healthcare, education, technology and financial services, while Forbes magazine called it one of the cleanest cities in the world. of_Pgh_CAFR_Final_2002.pdf" target="_blank">2002 Financial Statement Retrieved on January 30, 2007. Robotics, for example, is such an emergent sector of the local economy that the _Wall Street Journal dubbed the city "Roboburgh." The Private Sector: All signs point to Roboburgh

Pittsburgh is the principal cultural and economic influence in the eastern Ohio River Valley. Also, though the city proper is diminishing in population, some areas of the Pittsburgh metropolitan area continue to grow. Because of its low cost of living, economic opportunities, education, transportation and medical infrastructure, Pittsburgh is consistently ranked high in livability surveys. In 2007, Pittsburgh was named "America's Most Livable City" by Places Rated Almanac.