The Funderdome is a map in Plants vs. Zombies: Battle for Neighborville. It is where Battle Arena is held. It also the location of the boss fight against Olds Cool in Town Center, when playing as a plant.
Its name is a portmanteau of "fun" and "Thunderdome," a gladiatorial arena in Mad Max films.
As of recently, the Funderdome map was changed to be bigger. It also alternates between having water, hot cheese, and bouncy ooze as an obstacle.
Olds Cool Boss Fight
The Funderdome when a player fights Olds Cool is much different from the one in Battle Arena.