Rock Creek Caverns

Summary
The Rock Creek Caverns are located in the east/southeast portion of the Capital Wasteland. The Caverns are accessed through a sewer grate at the bottom of a radioactive-water filled crater that has exposed the sewer system, just to the west of the National Guard Depot. The sewer network is attached to a short segment of the Metro system, which then descends into a cavern system filled with Mirelurks, Mirelurk Hunters, and Mirelurk Kings. There is lots of water - a Radiation Suit or Advanced Radiation Suit is advised, if you're worried about -1 rad/second radiation.

Loot
In no particular order (except on the map - see inset), here are places of interest:
 * Walk up the fallen stalactite at A, which rests at an angle against the inner mound of the first, largest chamber of the Rock Creek Caverns. Don't jump - just walk right up along top of the fallen stalactite. At its tip, jump up to where some mushrooms are. Then continue around to...
 * B, where there is a hidden cache including a First Aid Box, Grenade Box, and Nuka-Cola Quantum. FWIW, when you first enter the main chamber (where the player is, in the inset), you can see the mushrooms at this location, high up and a little to the left, but you can't see the glowing Quantum.
 * At C, there is a car high up on a ledge, apparently due to a sinkhole from far above, judging by the scrap concrete on the cavern floor. Turning off clipping shows that there's no way to get there, nor any loot... but it can be fun to shoot a round into the car, and watch it go boom. The car shoots off the ledge when it explodes, and a Mirelurk King (King may depend on your level) waits below it. When the car explodes, it does ~20% damage to the King (6/30 VATS health bars gone), but actually getting the falling car to hit the King may not be possible (see Talk).
 * D is a minor collection of loot, with a Safe, Grenade Box, Toolbox, First Aid Box, and a usable Bed. In the inset you can see a squiggle going northwest from D - this is an uphill tunnel with a drop-off, a one-way passage to...
 * E, a nest of about a dozen Mirelurk Egg Clutches.
 * F is the real score in the Rock Creek Caverns, with a number of dead adventurers and wastelanders, a Laser Rifle, Laser Pistol, Power Fist, two Ammunition Boxes, a Safe, and miscellaneous other junk.
 * G is a break-through into a small segment of another Metro tunnel, where a small family met a sad demise in the chaos of armeggedon. Too bad they weren't carrying anything worth looting.

There will be plenty of caps from the Hatchling Mirelurk Meat (~13 at 4 caps each), Mirelurk Meat (~18 at 20 caps each), and Softshell Mirelurk Meat (~6 at 30 caps each), from both the Mirelurks and the egg clutches at E. Results may vary by level, but this haul (by a level 12 Vault Dweller) totals ~600 caps.

Associated Random Encounter
There is a random encounter where three adventurers are attacked by a Deathclaw. If you save them, one of them will give you the location to Rock Creek Caverns. Even if you just run from the (heavily injured) death claw instead of helping them you will get the map if the main adventurer is still alive to talk to. For more info, see Random encounter.