Curated OER
Bluffton College: Mausoleum of Hadrian
Brief description and photographs of the Mausoleum of Hadrian.
University of Chicago
University of California: Mausoleum of Hadrian
This site from the University of California contains a brief section of information on the Mausoleum of Hadrian, also with pictures. Not too in-depth, but rather interesting to check out.