The exteriors of the museum scene were shot in New York. The interiors however, were shot in the Philadelphia Museum of Art (note the griffin logo on the map Angie Dickinson checks, it's their logo). The large gorilla painting that she views (called 'Reclining Nude') now resides in the office of the wholesale and retail operations manager of the museum.
After Liz grabs the razor that Elliot drops in the elevator, she begins to running toward the screaming housekeeper, with her purse left on the ground in front of the elevator door. As Liz leaves from the apartment door the housekeeper goes into, her purse now appears over her arm.
Once the action heightens during the museum sequence, and we have now switched from tracking shots to steadicam shots, there is one steadicam pan in particular (from Dickinson's point of view) that reveals the on-set lighting equipment at the top of the frame.
What are the differences between the R-Rated version and the Unrated Version?
A
For Brian de Palma's provoking thriller about a razor-swinging sexual offender some shots of naked skin and several details of the murders had to be cut in order get the R-rating.
A detailed comparison between both versions can be found here.