Here is the price list for Arenas:

Basic Arena: 8 million gold or 5000 credits
-- 40 rooms, comes with ability to Duel.

Bait-the-frog: 2 million gold or 1250 credits.
Freezetag: 2 million gold or 1250 credits.
Freeforall: 4 million gold or 2500 credits.

There will eventually be more events that you can add on, as well as some modifications which will be significantly cheaper (things like no flying, and so on).

Currently an Arena may be owned only by an individual or a city. Understand that if an Arena is bought for a city with credits, IT IS OWNED BY THE CITY. The people who contributed credits have no more right to that Arena than anyone else. They have no ownership in it beyond any other player. If an individual buys an Arena for himself, only he or she may initiate events in that Arena, but it can never be taken away from him or her.

If a person or organization wishes to purchase an Arena, please send details to sarapis@achaea.com.

Penned by my hand on the 13th of Scarlatan, in the year 277 AF.