The first thing to consider in building a base is where is it located? A base might be in a city, or it might be located on the outskirts a safe distance from the city. The base could be some distance from major cities and towns. Such a location provides more privacy but makes the base less accessible.

Of course, the base could be even more distant: deep underground or underwater, or hidden away in a distant place like Antarctica or Tibet. It might not even be on Earth, located in orbit, on another planet or even in a distant galaxy.

Generally speaking, hero bases tend to be closer to the people the heroes work to protect, and are accessible to the public in some way. Some heroes prefer to keep a low profile and don't publicize the location of their base but they remain close to places where they're likely to be needed. Villain bases are usually hidden or located in distant places where they can't easily be found or attacked.

Structure

Once the location of the base is chosen, ask: what is its structure? Is it some fairly ordinary structure like a house, mansion or office building, or is it something more elaborate like a castle or underground complex, or even an orbiting satellite, moonbase or Dyson sphere?

The GM should consider the abilities and resources of the owners of the base. Could they create or acquire such a base? The designer of the base (the player or GM) may wish to draw a map of the base to get a better feel for the structure and layout, as well as what other features might go into the base.

Features

A base is assumed to come with all the normal amenities of a decent house or office: living room, dining room, office space, bedrooms, furniture, and so forth. It has utilities, heat, light, and such, and a reasonable amount of space. Everything else is considered a feature and must be purchased separately. The different features are listed below.

Backup Power: A backup power system, able to take over if the main system is damaged in any way.

Concealed: The base is hidden from casual sight by some kind of camouflage and/or its location is not generally known.  A concealed base usually has its own power plant, to prevent people from locating the base by tracking its use of power and other utilities.

Isolated: The base is isolated from the rest of the world in some way, making it more difficult to reach. It may be deep underground, underwater, in a distant place (like Antarctica), in outer space, on the Moon or even in another dimension. An isolated base must have its own power plant and must be sealed if it exists in a hostile environment.

Communications: The base can communicate via radio and TV waves (or one other means of the owner's choice). Each additional means of communication (like a hyperspace relay) is an additional feature.

Computer: A computer capable of processing information from a library and running the base's systems. As an additional feature, the computer can be artificially intelligent.

Danger Room: A room capable of creating various holographic threats and traps for training and testing purposes.

Deathtrap: The difference between a deathtrap and a defense system is generally that the deathtrap pulls no punches; it tries to kill you. Villain bases may have many different deathtraps as part of the defense system, or reserved for putting captured heroes in.

Defense System: A defense system provides the base with weapons it can use to protect itself from intruders.

Dock: A facility for storing and maintaining water-vehicles like a boat or submarine.

Firefighting: Automated systems for snuffing fires inside the base.

Garage: A facility for storing and maintaining various ground-vehicles.

Gym: A fully-equipped gymnasium with weights, gymnastics equipment, sporting gear, track, and so forth. It includes weights or weight-simulators designed to test the Physical Strength of any user of the base.

Hangar: A facility for storing and maintaining air-vehicles of all kinds.

Infirmary: A medical facility for treating injuries, illness and other maladies.

Lab: A facility for performing scientific tests and research.

Library: A storehouse of information. This may be actual books and paper records or computer files (or both).

Mobile: The base can move under its own power, like a vehicle.

Power Plant: The base can generate its own power, rather than drawing on outside power. The power plant may supply all of the base's needs, or it might be kept in reserve, in case outside power is cut off.

Prison: A facility for holding people captive. It includes power-dampners or other measures to hold super-powered prisoners.

Sealed: The base is independent of the outside environment and has its own air, food and water resources.

Security System: The base has alarms and sensors designed to detect intruders.

Sensors: The base can visually detect things inside and outside (using closed-circuit cameras or something similar). Each additional sense is another feature.

Staff: The base has a staff of personnel to take care of it and the needs of its residents. This may be a single very efficient butler or housekeeper, or a full staff of specialized personnel.

Vast: The base is much larger than a mansion, castle or office building. It may be a tesseract, larger on the inside than it appears outside, or it might be a huge installation, perhaps even an entire world or dimension.