Using Google Earth it is possible to explore extensive trench systems of the Iran-Iraq War (1980-1988) The resolution permitting it is possible to distinguish different types of field fortifications. Read:
http://www.historydigg.com/node/781
Interesting stuff isn't it. For the development of a scenario about the Golan Heights, I use Google Earth for the precise layout of all the Anti Tank ditches. Lots more to be seen though. North Korea is also interesting to look at.
Some WW2 trenches in Holland can be found with GE as well.
Huib