This place doesn't appear to be a big area. They have many caves and houses though, which wills it all up.
In Earthbound, this area is small, with nothing big going on inside of it. It is home to a Doctor Saturn, who is also known as the Healing Saturn, and a Hotel Saturn. It has little "houses" that are designed to look like the heads of Mr. Saturns. This version has a few caves, with only one having any significance throughout the game. One has items in it, one has a pathway to get to the Saturn Shop, and one leads to the Third Your Sanctuary Location. This area is ruled by Master Belch. He takes them all as slaves. There is a cave that you have access to after beating him, which houses all of the enslaved Mr. Saturns. This location does not appear on any map in the game.
In Mother 3, this area is still very small, but a little bit bigger than the Earthbound Version. Here, there are a few caves, but none of them have much significance. It, like EB, does not appear on any map. North of this area is Fire Mountain, where Phrygia and the fourth Needle lies.