Rock Creek Caverns

If you explore the extreme North past MDPL-21 Power Station, you'll see three adventurers being attacked by a Deathclaw. If you save them, one of them will give you the location to Rock Creek Caverns. You may also encounter this group in the Temple of the Union after the slaves have departed.(This is a random Encounter, and can happen any number of places)

The Rock Creek Caverns are located in the east/southeast portion of the Capital Wasteland. It is located west of the National Guard Depot.

The Caverns are accessed through a sewer grate at the bottom of a radioactive-water filled crater that has exposed the sewer system. The sewer network is attached to a short segment of subway system, which then descends into a cavern system filled with Mirelurk, Mirelurk Hunter, and Mirelurk King creatures. There is lots of water - a Radiation Suit or Advanced Radiation Suit will come in handy. At the end of the cavern system, there are a number of dead adventurers and an ammunitions cache, with a (among other things) Laser Rifle, Laser Pistol, Power Fist and associated ammunition. Also near the weapons cashe is a outcrop of scaleable rocks which will lead up to a Nuka Cola Quantum. The actual treasure is most likely the valuable Mirelurk Meat (valued at 20 caps ea.) and Softshell Mirelurk Meat (valued at 30 caps ea.), which can often be found in the eggs sacks littering the floor of the tunnles.