The building is a small cellar. It has a set of stairs on the eastern side leading to a small platform above where a Join the Railroad holodisk can be found. The cellar features several closets and mannequins. The store sells an assortment of pre-War clothing, as well as more useful items such as bobby pins and hazmat suits.
Fallon's Basement appears only in Fallout 4.
Behind the scenes
"Fallon's Basement" continues the pun on the well-known real life New England department store chain Filene's, whose discount locations (originally located in a sub-level of the flagship Downtown Crossing store) were branded as Filene's Basement.