Fallout: New Vegas locations project
The mess hall exists out of 2 sections, the first being the diner as you enter. Some tables, a jukebox and a Sunset Sarsaparilla vending machine. Next to the counter, with behind it Jas Wilkins, is a doorway to the kitchen. It has a fridge, shelves and a counter with some meat on it.
A Sunset Sarsaparilla star bottle cap can be found on the table with a lantern and empty Sunset Sarsaparilla bottle on it, directly ahead when you enter.
On the counter behind Jas there are a few strange meat pies. This would suggest that some of the meat she serves is actually human meat.
The mess hall appears only in Fallout: New Vegas.