Arboretum

From the Introduction:

Sunlight and a slight drizzle of rain falls into the room through an opening in the ceiling at its center, just above the two small trees growing in a patch of grass covered earth there. As far as arboretums go it is not terribly impressive, but for the inhabitants of this place it probably provides a welcome change from stone walls and floors. Clear water has collected in shallow, ankle deep pool around the trees and benches fashioned from brass and wood invite the wary to sit down and take a short rest. Wooden doors flanked by stone columns in all four walls of the room lead to other rooms.