The quarter-mile track hosted up to 15,000 spectators
Campaigners are in a race against time to raise £250,000 to buy the site of a major Roman find in Colchester.
The remains of a chariot racing track at the town's former Garrison were discovered under the former sergeants mess by an archaeological dig in 2004.
A local consortium has so far raised two-thirds of the funds to buy the land from developer Taylor Wimpey.
With no public funding available, private donations are now being sought to meet the 31 January 2010 deadline.
The group say they intend to buy the Victorian building and its gardens to create an interpretation centre, a permanent home for the Colchester Archaelogical Trust and other visitor facilities.
"This is our Roman heritage, not just for Colchester, but Essex and Britain," said Wendy Bailey, chairman of one of the consortium's partners Destination Colchester.
"This is the only Roman circus in Britain that's ever been found and it's bigger than the one in Rome, it's so vitally important."
She added they are trying to find over 200 people who can donate a minimum of £1000 each.