Fallout 3: Six Hours of Exploration

IGN's Fallout 3 week ends with a look at exploration, which includes a text preview, a video preview, and new screenshots.
As you approach the tower, you'll meet Roy Phillips. Roy falls under the ghoul and zombie class of characters. These folk have been so damaged by radiation that they're hardly human any more. There are two types of ghouls, though most humans think of all of them are worth eradicating. Some ghouls have lost their minds and become feral. They'll attack anything they see and need to be put down. Others still have a shred of humanity and can still think and behave normally. Their appearance, however, is enough to damn them in most people's eyes.

Once inside Tenpenny Tower, I found out that the local law enforcement not only hates Roy Phillips, they want the whole cadre of ghouls dealt with. I, of course, accepted the quest and went in search of the entrance to the tunnels the ghouls live in. At the heart of the tunnel, after fighting numerous feral ghouls, you'll find Roy and his friends. You don't have to kill them, of course. If you decide to talk to them and befriend the troupe, you can go on a series of quests with some very cool rewards, according to Bethesda, that I won't spoil here. I just killed them and went back to Tenpenny Tower for my reward.

With the ghouls dealt with, I turned my eyes towards the southeastern corner of the map. This is where the ruins of downtown DC sit with Rivet City right at the heart of it. There was just one small hang-up. At this point I had been playing for roughly four hours but had only leveled my character up to around level 5. This progression rate is pretty normal from what we're told, but it didn't make my trek any easier. The heart of Washington DC contains the nastiest enemies I've yet seen, roaming its streets with the all of the confidence being a super mutant brings.
Also mentioned is that Fallout 3 uses invisible walls at the map limits.