Building and destroying a metropolis in the underworld

vs631

I feel like the limited amount of space in the underworld would give attackers a disadvantage.
Limited space to set up siege weapons would be the main concern.
Opinions?

Noaani

Since the developers have full control over how much space there is in the underrealm, they can open it up so that there is as much functional space for a siege as there is above ground, if they so desire.

Jahlon

The Underrealm is 100 km²

A Metropolis is 0.5 km in diameter

If we add another 0.5 km in diameter for the siege equipment placement, or even a full extra 1km in diameter so there is a nice border, that still leaves us a LOT of room in the Underrealm!