This semester we have visited the Archives at Penn several times. This is an amazing resource! The Archives are located below the Fisher Fine Arts Library. The entrance is located just off 34th street by the crosswalk between Morgan and Fisher.
The Archives are always open and often have exhibits. As a class we have gone to see several of these including geologic mappings, a Robert Venturi exhibit, and the Laurie Olin exhibition of drawings. Laurie Olin even came in to walk us through his understanding of gardens and his growth and process of drawings.
I love visiting the archives becuase everytime I go in I come out with ideas and references. From color, style, drawing types, process etc the archive is full of ideas about what design is or was.
If you come to visit Penn I would definitely recommend stopping by the archive for a quick peek at the exhibit on display. It is always a wonderful experience.