I think the largest surface area would be Lumberton Bluff, located to the north of the Arrival Town (Lumberton Harbor). If you head out of town, just as you come out of "maze of twisty turny passages", turn left along the bluff face. You'll come to a wooden Ramp that works its way up the side of the Bluff. At the top, is the Lumberton Bluff Claim that you can purchase (Hydrocoins). You'll need to perform some initial mining in Dawn Rest, in order to earn the funds (Hydrocoins) needed to build it out. Digging down by hand is very difficult and takes a LOT of time. So you'll need to explore the Island a bit and earn some of the Island's special coins (cannot remember what they're called offhand) and get to Moxx Island, which is a small island just off the coast. You'll need to purchase a Pass to travel there, where you can purchase certain vehicles. This will all take various forms of funds in at least two different currencies, and requires some knowledge of operations on Volcalidus Island.