I was thinking about Alien Bases just before and came up with a few questions:

1. What would the surface of the base look like? They have no defenses or hangars, so the only external sign of the base would be the entry point/s. What do you suppose it would look like? There you go Hobbes, a new terrain item for you play with!

2. Why do they not have hangars? Does this mean UFOs never need to "park", or do they just return to Mars to refuel etc? How do the Supply Ships get their goods into the base with no hangar to enter in to? Does this mean that the Aliens do indeed have teleporting technology as the intro shows?

Okay, so there's more than a "few" questions

The ships park outside.

I assume the bases are hidden by holograms or something.

Maybe a landing tarmac (even though the ground assaults just have the local terrain )

Almost the same as an X-COM base. The only thing that is above ground in an X-COM base is the access lift. The hangars are also underground but there must be an access point somewhere since the aliens will pop in through them. So one access lift point as well as an access point for each hangar.

What would it look like? I guess those points have to be camouflaged somewhat to prevent the general populus from wandering in for an impromptu visit! On the other hand, they have to be somewhat visible above ground because your soldiers and the aliens can find them rather easily.

The alien base does not have a hangar structure. The only access points it has are the 2 green "staging" rooms. This must be their "Access Lift" structure, for transferring supplies, weapons and new troops to the base. Since no UFO's are ever stationed at an alien base, and there is no "hangar" structure for repairing/refueling the UFO's, logic dictates that they limp back to where they came from in case of repair, or the dreaded "out of Elerium" fuel warning!

The bases seem more like supply stations rather than actual a place to stage combat. That is if you take the view that some supply ships stop by the base to pick food up. It's a habitat, green house (although that's stretching the term, as they seem to grow subterranean plants that don't really need much light - unless there can open up the roof to let light through from time to time or they have heat bulbs) and storage facility (such as that hall with the guard tower overlooking the nutrient vats). The command centre is there to oversee that everything runs smoothly.

The 'activity' that the base generates could be raiders, who, on foot, steal resources from the nearby surroundings.

But then there are those purple rooms inside the base that might just act as service bays. Too small for anything but the small and medium scouts though.

- NKF

Maybe X-COM use that ground-penetrating radar stuff to find the bases! The same techniques that Archaeologists use to find buried, ancient cities

... or they could just follow the Supply Ships and see where they stop

I'd agree with the opinion that they would be camouflaged.....maybe a nice green pasture overhead, with plenty of grass for cow-attracting.

Maybe that's how they're detected: by the increasing reports by farmers of missing cows coming from a certain area.

Maybe I should make a cow smily.

It seems obvious that craft land outside the base. All the supply ship raids I've done come to mind.

I think that there is a small docking bay that is in the ground, like a small room or something, that the craft will dock with, get supplies, and move on away

don't forget, the ships have those transporter pads, so they can just hover over the base and grab what they need.

Which transporter pads?

I think he means the red lifts.