Vault 92 and Old Olney
The northeastern corner of the map, near Old Olney. It was part of an experiment conducted by Vault-Tec Corporation to create supersoldiers. Officially, all talented musicians were invited to the vault with the stated goal of "saving musical talent." However, when the vault closed, its population was exposed to white noise. The experiment was a success until one of the "guinea pigs" went crazy and tore three people apart. About a third of the inhabitants followed suit; they then killed the rest of the vault's inhabitants.
The approaches to the vault are protected by mines. If you enter "Cacophony of Sound" into the terminals in the Residential Sector, you can destroy all the mirelurks in the area (if you refuse to earn experience). The vault is home to numerous mirelurks, Combat Mirelurks, Royal Mirelurks, Ghoul Flies, and Roaches. The vault's layout is fairly simple; a certain amount of ammunition, weapon assembly parts, medicine, and other items are collected. The violin is in a recording studio, the door to which opens from a computer in another room.
Trophies: When Agatha gives you a quest, she also hands over the keys to a weapons chest, which contains various ammunition, including Mini Nukes and rockets. If you bring Agatha the sheet music in addition to the violin, she'll give you a Magnum Blackhawk revolver (D58, AC6, A .44 Magnum) (one of the most powerful in the game) and 12 .44 Magnum rounds (you must ask for the reward, the second conversation option!).
Old Olney
Information about the location can be obtained at the Nuka-Cola Factory by entering through one of the terminals. There will be a note there, "Nuka-Cola Supply Chain," and PB 3000 will mark the location on the map. The town was invaded by Deathclaws, who slaughtered the entire population. Aside from trophies from the dead bodies, the only other things worth exploring are the Old Olney Sewers and the body of Carl Wallace (a nod to "Wallace and Grommit"?). Wallace was a truck driver who delivered Nuka-Cola during the Great War. His skeleton lies near the town's fire station. Nearby is a note explaining how the accident occurred and what was in the truck. The truck itself contains many bottles of Nuka-Cola and several bottles of Quantum Cola.
The Sewers can be accessed either through a hatch on the western side of the city or by falling into a trap where a collapsed metal structure blocks the exit. It's one of the highest concentrations of Deathclaws in the game. Recommended weapons include either a flamethrower, which allows you to engage multiple powerful enemies in a confined space, or a Dart Launcher, which slows the Deathclaws' movements and gives you time to engage them with other weapons.
Trophies: Prototype Medical Power Armor (DR40, W45, +25 rad resistance, -2 Agility) injects the hero with Med X if this drug is in the inventory. It has a personality and speaks in Mr. Gatsy's voice); the book Duck and Cover (at the very end of the same cave, under the skeleton); the nuclear grenade launcher "Fat Man" (can be randomly found in one of three safes in the southeastern storage area in the sewers).
Source: stopgame.ru, thenthapple
See also:
Evergreen Mills
Jury Street Station
Farragut West Subway Station