First of all, look at the main map from the HART. Double click a continent with a yellow flashy thingy on it. Look on the continent map in the general position that the yellow thing was on the main map for a thing called "Geowarp" (NOT and inactive one)
HART to that position. Voila one geowarp. Geowarp are the entrances to the caverns.
One more thing, you have to have Core Combat to get to them.
Unfortunatley, as spee said, once you enter a geowarp for the frist time, you will be posed with an IQ test which oyu must complete. If you fail, you will loose 200 exp points. (you know, kind of like the America's army Medic exam)
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