Last Drop, L4D map release date and video
Last Drop is a survival map for Left 4 Dead, of a finale of a 5 map campaign for Left 4 Dead. The survivors have barricaded themselves at a Gas Station in the hills near Riverside, how long will they hold out?
On Friday, October the 16th, you should get prepared to fight the horde and jump on the roof of the gas station that the map is centered around.
Source: Official Website