Metropolitan Museum of Art
Metropolitan Museum of Art: List of Rulers: Roman Empire
This website offers a list of the emperors of the Roman Empire, separated by dynasty. In addition, you can click on pictures of art and architecture of each dynasty of the Roman Empire to get information about them.
Wikimedia
Wikipedia: Trier
Wikipedia, a publically-maintained wiki, offers information on the German city of Trier, including its well-preserved Roman buildings, city gate, and baths. There are images and external links, as well.