Stable 17 is, to date, the only known Stable built under water. One hundred and fifty metres down at bottom of Lake Eternity, Stable 17 is a control stable that utilizes geothermal vents and other natural resources such as gasses that are released at locations of volcanic activity, rather than conventional power systems.
It is also the site of Project Nightmare; an experiment run by Stable-Tec looking into the unique effects of an unknown electromagnetic anomaly believed to be part of the meteor that crashed into Equestria shortly before the rise of Nightmare Moon.
Stable 17 comprises of eight main sections linked together by partially submerged tunnels on the lake floor. The main sections are:
- The Core: The main section of the stable which contains living quarters for all residents, security, food court and exercise facilities. It also contains the exit tower which must be raised up to allow the residents to exit the stable. [Back and centre of image]
- Maintenance & Systems Control: This section contains power management, life support, water filtration and gas filtration. [Dome mid-centre near the Core]
- The Orchard: The primary food supply for the stable, the orchard is a vast structure that supports around two thousand apple trees of various ages and varieties. It has a unique Season Replication System created by the MoA; a favour for Scootaloo from Rainbow Dash, which allows for year round harvesting and other possibilities for resident relaxation. [Rectangular building next to Core]
- Geothermal Turbines 1-3: The three turbines that provide most of the power for stable 17. Turbine one is the largest with a blade diameter of 25 metres. Turbines two and three are smaller with a blade diameter of seventeen metres. [Turbines 1-3, Right to Left]
- Algae Processing: The other source of food for stable 17. Grown on the nutrient-rich rock at the bottom of the lake, the plant grows a thick layer of algae that it harvests periodically. This is then used to bulk up and add extra nutrition to the food cooked in the Core. [Far left dome]
- Gas Syphoning: The smallest section, the Gas Syphoning section is located on top of a natural gas vent. The supply is almost limitless, as the gas is produced by the geothermal and tectonic activity below. [Small far dome, back left]