Center City Tower
This building, one of the few supertalls ever proposed for Philadelphia, would've risen on the former Meridian Tower site on 15th Street near City Hall. Designed by Kling (behind Philadelphia's Bell Atlantic Tower and Yokohama's Landmark Tower), the building was initially pitched to Comcast as their new corporate HQ which, at the time, was in Centre Square directly across the street.
The building never got past the proposal stage as the site was entangled in a protracted legal battle between two separate developers, during the course of which another site was pitched to and ultimately accepted by Comcast and is now Comcast Center. The original site is now partially occupied by the newly completed Residences at The Ritz with the remaining half slated for 1441 Chestnut which has begun sales.