Building in which the events of the adventure Night Floors by Dennis Detwiller in Delta Green: Countdown takes place. It also features in Detwiller's Insylum RPG as a location within The Night World (where it may be spelled MacAllistair, although this may be a copying error by the creator of that page). The following description is taken from Night Floors (which should be consulted for more details).
It is a three-storey brownstone building built in 1924 in Manhattan, New York with a faux-castle design and home to several arty types. However, after Abigail Wright came across a copy of The King In Yellow, it has not been right, gaining the addition of a decidedly abnormal new set of levels, The Night Floors. It is owned by a not-for-profit organisation called ARTLIFE which provides accommodation for artists.