Nuken was a map specifically designed for the game mode Siege. This map is set in a nuclear facility and has a linear design in which the Scorpion Tank must travel. Nuken was the only map made for Siege mode. Along the road, there are several barriers that must be lowered so the Scorpion Tank can pass through. When the Scorpion Tank was reached the final area (a trailer attached to a truck), the attackers will win.
The map is designed so that each team has a 'base' they spawn in and is inaccessible to the opponent (and to yourself, once you have left it).