Tol'Viron Arena is located in Uldum, and was introduced with Mists of Pandaria. It is the sixth arena map, and the first arena to be introduced since the Dalaran Sewers (not including the revamped Ring of Valor).
The map's design is based on the simplistic Nagrand Arena. The only difference between the two arenas is the art style and the direction of the pillars.
From the World of Warcraft Preview Panel: Mists of Pandaria article:
Added in Mists of Pandaria, the Tol'Viron Arena (previously referred to as "Tol'vir Proving Grounds") is an arena in Uldum modeled after the arena in Nagrand.