US Geological Survey
U.s. Geological Survey: Building Stones of Our Nation's Capital
Pictures and text describe the source and appearance of many of the stones used in the buildings and monuments in Washington, D.C. Included are a geologic time chart and an illustrated map of the geologic and geographic features of the...
Tech4Learning
Pics4 Learning: Images for Education: Castles
A treasury of photos of various castles from around the world! Although the images do not contain much information, they can be used as a visual reference for students of all grade levels.