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 little family met their sad demise in the chaos of Armeggedon. Quite sad - especially because they weren't carrying hardly any loot.

The Rock Creek Caverns also offer plenty of caps from 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 will vary by level and pure randomness; the haul detailed here (by a level 12 Vault Dweller) totalled ~600 caps.