How many bowling lanes do you think would fit? Of course, the problem with toppling pins and wayward balls will have to be solved first (not to mention pressurization. Might also work as an archery range.)
Ok then, how about a nerd question: what are those green hoods/scoops/vents on the side walls for?
Inspiration, move me brightly! Light the song with sense and color. Hold away despair, more than this I will not ask. Faced with mysteries dark and vast, statements just seem vain at last. Some rise, some fall, some climb, to get to Terrapin!