Me and my older brother who used to chum around with back then when we were kids, we loved anything to do with Sasquatches(bigfoot), and the writings of Erich Von Daniken. Well unless some new technology comes around to find and/or map these caverns or tunnels from the surface, we'll never ever know what for certain what is down there in the what first 20 or so miles of crust they say we have before it turns to lava.