The entrance to Arco B cave in Northern Spain.
Imagine this. You are squeezing through tight passages where your body barely fits. You are surrounded by darkness and navigating by torchlight. If your light dies you are stranded.
Seeing some of the ancient art sites is not easy work. Just look at what a leading Spanish anthropologist is willing to go through in order to document paleolithic art in the Northern Spain. Being underground is hard. It is dark, it is often cold and wet. It is an inhospitable realm.