This is Creswell Crags, a gorge full of magnesian limestone caves, that were occupied during the Ice Age.
According to the guide, about 60,000 years ago (about the time modern humans were arriving in Australia), there were Neandertals living here, along with hyenas, mammoths and reindeer. Then it became too cold until about 15,000 years ago when modern humans took up residence.
This is the largest of the caves. The entrances we went into, complete with our hats with torches on them, is along a bit futher.