UFO crash site

The UFO crash site is an unmarked location in the Commonwealth in Fallout 4 just east-southeast of Oberland station. However, there won't be anything there until the UFO crash occurs at level 20.

When traveling around, the Sole Survivor may hear the sound of a crashing plane. The start of the event is a random encounter, and, as such, the chances of it happening are random. It may even happen at a long distance away from the crash site. A ship will then pass quickly by overhead before crashing in the distance. Actually seeing the ship might be difficult because of how quickly it is moving, but it does leave a short lived, but distinct, trail of smoke. The explosion is usually too distant to see, but is very loud nonetheless. The ship always crashes in the same location.

Alternatively, if the Sole Survivor activates Relay Tower 1DL-109, a radio signal titled "Garbled Radio Beacon" will be discovered. If the Sole Survivor tunes their radio to the frequency, they can travel east and the signal will resolve to a higher quality until the Sole Survivor discovers what appears to be a crashed alien vessel.

Layout
The site features a half-buried UFO in a hillside with a skid area of destruction including broken trees, flattened ground, and scattered flames. The trees all around will be permanently on fire, making the location easier to spot from afar. There isn't anything particularly valuable about the crash site itself (no way to enter the UFO, nor anything to scavenge at the crash). Next to the still burning UFO is a trail of green blood. The Sole Survivor can follow the trail of green blood, slightly north, down into a ravine, and then into a nearby unmarked cave.

Inside the cave is an alien with an alien blaster pistol and 400-500 alien blaster rounds. If the alien is targeted in VATS, it will show that its right leg is crippled, presumably a result of its apparent crash landing. On sight, the alien will immediately attack the Sole Survivor. Next to the alien is a human skeleton and a Ham radio which is the source of the nearby garbled radio beacon. Turning the Ham radio off will cause the beacon to turn

Notable loot

 * Alien blaster pistol

Appearances
Crashed UFOs have appeared in almost every version of Fallout; The first crashed alien ship appears in the original Fallout, the developers had planned a crashed UFO for Fallout 2 but none was included in the final version, although there was a random encounter with a crashed "Star Trek" styled shuttle craft. In Fallout 3 there was a very similar Alien crash site, and in Fallout: New Vegas there is also a crashed alien recon ship (although it is inaccessible). Most alien encounters had been included as easter eggs and were non-canon until the release of the Mothership Zeta add-on.