The Garden is a natural cavern under the surface of the Moon, a steam bubble that resulted when a big comet hit the Moon and formed the crater Mare Stellatis is built on. The impact resulted to lava tubes and the presence of water, which was the reason why the Farside Colony and Mare Stellatis were built there.
The cavern is shaped like a flattened teardrop, at least a km high and many across. Suntubes and shafts connect the cavern with the upper floors of the City, and a fireman's pole traverses from those levels to reach a meadow.
The Garden forms an ecosystem of flora and fauna full of rich organic scents and its air is warm and moist. The Watercave, a lava opening 1/5 of the way up the wall, supplied by condensed moisture of the ecosystem, is the source of a cascading waterfall which feeds a lake. A pipe half a meter across juts from the shore and dives below the surface of the lake, its other end buried in the rocks at the base of the falls, is connected to the deuterium refinery at Farside Colony; the inmates fill it with the Downsider quota. The lake itself holds more than 2 years of water reserves.
A pump room is hidden beneath the rocks of the waterfall, shipping water through the pipeline. The flow gauge and the lake volume reader are the heart of the economy; the lake level has to be kept constant by varying the pump rate. The pump rate in turn dictated how much power Mare Stellatis could receive. The Checker takes readings to balance the water budget.
The management program simulated morning and evening by varying the intensity of the suntubes across the ceiling, with first light coming from the "eastern" suntube. With no seasons, and a maximum nutrient conversion, the crops were strictly defined by an artificial climate. When carbon dioxide levels are low, inmates light bonfires at socials, and when it is too high, they remove dead organic material.
Plants include a long peach, a canopy of hundred-meter cedars with impossibly thin trunks over lush tuftgrass and wildflowers, and a forest of fragrant pine trees and cultivated fields. The orchards were an eclectic mixture of citrous trees, vines, and tropical fruits. Vines and creepers spill down the sides of the falls The lake is filled with oversized lily pads.
The Garden is occupied by animals that were imported: rabbits, chinchillas, songbirds, chickens, deer and sheep (whose meat is reserved for special occasions, like the arrival of a newling). The lake contains perch and trout. Unwanted mice also found their way there, which are edible. Those who find their way to the City are caught by cats.
The ecosytem provides not only food but also life support, convection heating and ventilation in a much larger scale. 90% of the energy input goes to the suntubes. Plants renew the oxygen. Heat and moisture is carried through venshafts to the City; as it circulates, it cools and eventually the moisture condenses out; the cooled air from Upside filters through Downside until it comes through the Watercave, bringing the Downsider water quota with it.
There are also invisible sound sources that provide music.