The Senora Desert Structure is located southwest of the Sandy Shores airfield and due east from Harmony.
The structure is built into a hill in the desert, using similar assets to those of the Abandoned Mine Shaft, but there are extra wooden support beams on the outside. There is no trail or any signs that the structure was used recently, and no indication of what exactly the building was used for.
There is currently no way to enter it, as the large wooden door is immune to explosives and gunfire. The interior consists of a single hollowed out room only a few square feet in size, with nothing but a pile of rocks on one end of the room.
It is currently inaccessible and serves no actual purpose in GTA V's storyline.
Although they are not well known and are overlooked, fan rumors on the internet state that loud metallic noises, similar to the "skyquake" phenomena, can be heard while the player is near the entrance of the structure.
While the structure was initially speculated as being either another mine shaft or a shelter from alleged "skyquakes", due to the structures proximity to the airstrip and Sandy Shores (a 1940s-60s era residential area), the structure is now believed to be either a World War 2 era munitions cache or Cold War-era fallout shelter with the lack of detailed interior being the result of Rockstar's lack of an intention of making the structure accessible to the player.