Received from: Paladin Tristan [Citadel - A ring]
Walkthrough: Once you've ended your conversation with Tristan you must leave the Citadel. Notice that a new location has been added to your personal map - White House Plaza. Obviously you can't fast travel to that area, however you can start the game in front of the ruins of the White House or somewhere else nearby. Thankfully the plaza is going to be guarded by the Brotherhood of Steel. Find a hatch [#38] leading to the Utility Tunnels.
MAP OF THE TUNNELS:
Map legend: 1 - entrance to the tunnels; 2 - storage area; 3 - passageway to Pennsylvania Avenue; 4 - passageway to the Presidential Sub Level
You probably won't spend too much time in this first underground area. There aren't any enemies nearby, so you may take your time to look around. Sadly you won't find any cool treasures in these tunnels. The only exception is a small storage area found to the right of the entrance [#39]. If you look close enough you'll find a bottlecap mine (one of the objects you could manufacture using found schematics). Ignore the corridor located in front of you, because you would be dealing with dead ends and empty corridors. Instead travel through a blue door to your left. Eventually you'll get to a passageway leading to the Presidential Sub Level.
MAP OF THE PRESIDENTIAL SUB LEVEL - WESTERN PART:
Map legend: 1- entrance to the sub level; 2 - staircase; 3 - passageway to metro tunnels; 4 - passageway to the eastern part of the sub level
In this case you'll have to be ready to defend yourself against single enemy units. You'll start encountering enemies upon your arrival in the metro station [#40]. You won't be dealing with living hostiles, because instead you'll go against different types of machines, including sentry bots and security turrets. Don't forget to attack your enemies from a larger distance and avoid their most powerful attacks.
Once you've secured the first room move forward and eventually you'll get to the stairs [#41]. Obviously you must use the stairs to get to the lower floor. Keep heading forward, eliminate anything that will stand in your way and be on a look out for ammunition crates. Ignore the first metro tunnel, because it has collapsed and you wouldn't be able to reach your destination from here. Instead proceed directly to the second larger tunnel and be on a look out for Capitol signs. Start moving east and get ready to get rid of a small group of sentry bots along the way.