Blood Gracht is a Killzone 2multiplayer map with multiple layers. Close quarters combat as well as medium range, and an environment that'll suck you in. This map is good for Assassination, and will constantly make you hope the enemy isn't around the corner. It reappears with some aesthetic changes and modifications in Killzone 3, and appears again in Killzone: Mercenary.
The multiplayer map's name is similar to the Halo: Combat Evolved map Blood Gulch (one of the most well-known maps in the Halo series), however the actual map layouts are not even remotely similar. It's unknown if this is a reference to the popular Halo map.