Begetting Besiegers! The landing's siegery shop. It is also where I would personally recommend hosting the siegery battle.. Here is why:

[Begetting Besiegers, Sky Arena]
High walls rise up to encase this open arena in a solid cover, muting the sounds of the town to a quiet muffle. Moonlight from the open sky glints off the surface of tall flag poles, their banners stirring slightly with the breeze. The arena itself is a circular stretch of scuffed dark slate, surrounded by a set of wide stone steps which lead up to an observation deck.
Obvious paths: out
>go step
[Begetting Besiegers, Watch Deck]
A sturdy wooden observation deck stretches out in a half-circle providing ample room for spectators. A carved ironwood railing provides some leaning comfort to onlookers while they view the arena below. The tops of flagpoles rise up from the sides of the deck and stretch up into the night sky above. You also see some wide stone steps leading down.
Obvious paths: none

It has the sky arena with a spot where people can "watch arena" or "look arena" to see whats going on below.. great for when you have a huge audience. It also has:

[Underground Arena]
Crude wooden benches ascend in a semicircle around a smooth dirt arena where old blood stains have darkened the ground in many patches. Lit torches are scattered about the room casting flickering shadows along the stone walls. A pile of dismembered siege miniatures have been haphazardly left in a corner. You also see a flimsy wooden door.
Obvious exits: none

There are 59 minis for sale and 6 cases in this shop.. about 35k per mini. I would recommend JUST buying a regular mini, not a keep, catapult, ballista and the like.. for events we tend to just do one-on-one minis and not a full game, as the full ones take FOREVER. The more you play, and win, the better trained your mini is. That said, a well trained mini is NO guarantee of winning. The Enclave's last siegery event ended with Greganths insanely well trained rolton against Fulmen's bought that day off the shelf blacksmith. It was awesome.

I would also recommend not including s-class minis as they tend to be OP.