Gimbels-Philadelphia dedicated their sixth store, at KING OF PRUSSIA PLAZA, in May 1966. Some of its features were a beauty salon, community auditorium, upscale restaurant and snack bar.
Drawing from Gimbels Brothers, Incorporated

Gimbels and John Wanamaker connected into a 2-level, heated and air-conditioned concourse that was added to the north side of the existing open-air complex. This newly-built section was referred to as the Enclosed Mall.
Photo from https://www.valleyforge.org

In a circa-1973 physical layout, the Enclosed Mall is shown in light gray. The original open-air structure, or Outdoor Mall, appears in black. In its entirety, KING OF PRUSSIA PLAZA encompasses 1.3 million leasable square feet and contains 119 store spaces.

A small concourse, originally known as the Piccadilly Arcade, was sandwiched between the Penneys and Korvettes stores and provided a connection between the Enclosed and Outdoor Malls. By the early 1970s, this section had been renamed Continental Arcade.
Photo from www.flickr.com / "Djramone"