There are many stories OMJ of people and beings living beneath the surface of the earth. Here is just one short account for you:

Hopi legends described a race of "Lizard" people who, 5,000 years ago, built three great underground cities near the Pacific Coast, including one beneath Los Angeles. In 1934,a mining engineer W. Warren Shufelt went seeking the truth. He said that there was a city under Los Angeles, which was built in the shape of a lizard, that extended from Dodger Stadium to the downtown Central Library. It was supposedly built using chemicals to tunnel through rock. One version of the underground peoples demise, came as a result of natural gas leakage into their caverns. Shufelt talked of finding many tunnels and of finding treasure under Fort Moore Hill. He managed to get permission and started to drill holes, and a few were drilled but apparently there were many problems with cave-ins, so the drillling was stopped.
Shufelt was then said to have disappeared from public view.
Just prior to the drilling, Edith Elden Robinson(a psychic)reported a vision of "a vast city...in mammoth tunnels extending to the seashore."