Google World Wonders Project - Goodle has made 3D maps of World Heritage Sites so you can take a "virtual" tour of all of these - you can search by theme - castles, wonders of nature, location - North America, Asis, etc and there is an EDUCATION tab for teachers with lesson plans - very cool!!
Take your global kids on a panoramic world tour! 360 Cities features panoramic views of many of the world's great cities! Start by selecting the world map to choose a destination. You can even go underwater or venture out to Mars!