Time Team (a uK program) excavated a WWI bunker. They found some tools and stuff inside. One entrance was blocked by some ordinance. They left that untouched.
As part of some research into Col. Lawrence I undertook for some feature articles about two years ago, it turns out that the Hejaz Railway in Arabia was never really repaired after Col. Lawrence & Co. blew parts of it up; the engines and rolling stock were generally left where they were wrecked and are still there today in many places.
There are, however, restored sections of the line operating in Jordan and Syria, using some of the original rolling stock for the tourist trade.