Five major skyscrapers have been added to the Philadelphia skyline in the last ten years. The most notable being:
The Comcast Center
and Cira Centre
Here is a list of Philadelphia tallest buildings for anyone who wants to know what buildings they're looking at on the skyline.
Philadelphia City Hall was the tallest building in the world for only seven years after being built in 1901, but remained the tallest building in Philadelphia by "gentleman's agreement" all the way until 1987.