The Valley of Four Drafts is a valley in the Mortmain Mountains. The valley first appeared in The Carnivorous Carnival on a map that Madame Lulu had in her caravan. The map appeared not to have any significant points of interest until looked at closely, when you could see a coffee stain marking a valley in the mountains.
The valley was the main setting for book the tenth, The Slippery Slope. Located in the valley was the second-to-last safe place for V.F.D. members, however the headquarters were burned down once the Baudelaire children reached it, leaving the Hotel Denouement the last safe place.
In The Slippery Slope, Snicket suggests that while the headquarters in the valley were burning, the sugar bowl was thrown out of the window, and landed in the stream beside it, which heads out to the ocean.