The map works best on Half-Life 2: Episode One but can also be played in Half-Life 2: Episode Two.
This map was originally supposed to be for a multiplayer co-op zombie mod called Over-Run but the mod died without ever being released. Therefore as a single-player map the map has some alternative routes and a larger area that the player can freely explore. The map is a Ravenholmish town next to a small lake but there are wider streets and the areas are more open than in Ravenholm.
I've also made a commentary playthrough of this map. Go check it out.