Level Three is the crew health care and soft stowage area. Level three houses an exercise area with a treadmill and stationary bicycle.
Exercise is important to keep astronauts healthy in weightlessness for long periods.
In addition, this level contains a soft stowage area identical to level one. The Earth-viewing window is 20 inches in diameter and is located near the exercise area. The window has four panes totaling four inches thick and a hard frame around each window that attaches to all layers of the shell. Stowage Soft-sided cabinets provide stowage for spare parts, supplies, clothing, and other equipment. TransHab would double the stowage room available on the International Space Station.