DCTA Tunnel 014-B Potomac

 is part of the Metro system under the Capital Wasteland.

Notable loot
In the southernmost chamber (behind an underwater passage) is a D.C. Journal of Internal Medicine, guarded by a Mirelurk King.(Xbox 360-this editor found just a regular Mirelurk guarding said chamber and this author is a level 20.)

[confirmed on 360, as a level 19 player I found only Mirelurks and no Mirelurk king.

Glitches
Noticed in the Xbox 360 version of the game, the water near the Mirelurk Eggs of the Georgetown West exit sometimes glows a highly fluorescent toxic green color. This has also happened in other locations.


 * Confirmed with more details. It was normal at first pass (entered via Arlington Utility), but upon exiting to Georgetown and immediately returning the almost white glow was throughout the area. So it may be re-entering from bright daylight that causes the glitch. (Due to loading, at least on the 360, light settings may lag behind the scene by half a second. Especially funny is to fast travel from e.g. Megaton to an outdoor location and the day/night turns immediately to night/day respectively.)