Caves

Since I have determined that there will be levels of metal I feel that there should also be an element of difficulty to getting the high quality ore.  I think the best way to accomplish this is to have 3 levels of caves that run underground.  In trying to keep things random I could have it so sometimes the caves will connect, and sometimes they won't.  This means that someone will need to successfully navigate the caves all the way to the lowest level and then back again in order to get the high grade ore.  Since something else I want to implement would be land  mines, builders could set land mine traps, making entry into a cave even more challenging and dangerous.  Creating the network of caves will be a part of the land creation, which is still going to take a while to complete.