City Hall and the post offices mentioned are all Second Empire French, a very distinctive style which masks the actual number of floors in a building. The base of City Hall is 7 floors.
The Wanamaker Building is an old favorite of mine. Built in 1909 on the site of the previous Wanamakers (John Wanamaker coined the phrase "the customer is always right), it's Philadelphia's only Burnham building and the largest single building downtown by a margin, occupying its entire block.