The map size seems to be roughly the same as fallout 3 and yet all buildings are located on a narrow strip in the middle. A huge area which covers almost 30% of the map left of good springs is inaccessible and has has no locations except the add on. On the right there are almost no buildings once you cross the river. Even on top the locations stop short of the actual map space.

In fallout 3 the locations may have been scattered but there was something in all corners. You could set out in any direction and eventually find something.

So I was wondering why so much space in new vegas is left vacant?

The playable area of the map is actually slightly larger than that of Fallout 3, if I recall correctly. If all of that space outside it was available, it would actually be significantly larger than what we had in 3.

3 took place in an urban area, so it makes sense that it has more filled space than New Vegas, which primarily takes place in a desert. The biggest difference is that 3 was almost entirely flat, and there was virtually nothing to impede your progress from corner to corner (excluding downtown DC). In New Vegas, there are mountains and cliffs. It has more vertical to 3's horizontal, and because you can't wander aimlessly to the same extent, and have to take certain paths to reach certain places, an illusion is created that it is smaller, whereas in reality it is a little bit larger.

The main reason for me is that it's based on a real (albeit shrunk for gameplay reasons) area. Go to a map of Nevada and spot the areas used in game, there are quite a lot! What this means is that features like impassable mountains, areas of pure desert, etc are all there. One of the key differences between New Vegas and Fallout 3 is that efforts are made to make the game world as realistic as can be for the setting, i.e. no raider bases, houses, small towns etc in the middle of nowhere with no means of actually surviving. Whereas in Fallout 3 you couldn't move for raider, super mutant bases, effort has been made in New Vegas to explain what you see. A term used to describe Fallout 3 (rightly or wrongly) is "theme park", as in lots to see and do. New Vegas still has that but the focus is more on conversation, choice and consequence.

Fallout 3's map is square, New Vegas's is an irregular rectangle. The area west of Goodsprings isn't part of the map, it's just shown on the map screen because the screen is a square.

....because it's a desert. Have you ever been to the Mojave Wasteland in RL? Traveling to Vegas, you'll see exactly what the game is trying to display: a whole lot of hot, inhospitable, deadly nothing. The only thing odd in-game is that the sand is darkish orange/beach sand when in reality, it's as if the sun itself has bleached the entire place white and of life. And like David said, FO3 wasn't really focusing on realism, but rather on 'kewl' locations and crap.

Go outside the map and explore around. There's something like 2.5 times more territory out there, not counting the infinite ocean.

Not many locations though.

Well all the land on the east side of the river was supposed to have a bunch of legion settlements, but because Bethesda made obsidian release the game prematurely because they didn't want it interfering with their skyrim announcement and release, obsidian was forced to scrap a bunch of content in order to make the deadline.

It's actually a curse that has followed obsidian numerous times while working under a producer, which is one of the reasons they went to kickstarter to fund their pillars of eternity game, because now no one is lighting a fire under their ass to release the game as soon as possible.

Question because I dont have NV ... Is it still one large fluid map like in Fo3 , but having loading screen doors to port the player to interior cells and small outdoor world locations like megaton.

Although I guess the Downtown DC area is not a fluid map either ... so its as if a big chunk of the large square map is missing from the map that has wasteland cells stitched together.

From a modders point of view , Is it as if the NV map has left a crap ton of open space for you to build your own towns that will be seamless with no loading screens?

Thats pretty awesome if so. And seems similar to the world maps Novalogic created in their delta force series.

Even though they are just a map template of repeating terrain patterns, they are freakin huge.

I think they are roughly twice the size of the Fo3 DC map In 1 direction/dimension. So that would be spacially squared ... but thats just seems to me method.

if you are on the PC there are mods like AWOP that add tons of random places that make the wasteland feel not so barren and empty.