Ah, yes… the Imperial Army in the Warhammer 40K Universe fields a vehicle called the Hellbore, capable of finding its way underground and disgorging troops behind enemy lines. I guess other works of Science Fiction feature similar vehicles.
It is no wonder that this type of vehicle finds its way into Steampunk as well. It can be used to explore the earth right down to the core and it can be abused for military purposes.
Of course, the idea also makes images like the following possible: