Work to document the medieval remains of Norwich market begins on Monday.
Norwich City Council are behind the new market scheme
The current refurbishment of the site will lower the ground level by two feet and mean most medieval deposits will be lost forever.
Experts from the Norfolk Archaeological Unit will record any special features and finds.
The market, established between 1071 and 1074, is one of the oldest and largest in England. Its refurbishment will be completed by the end of 2005.
Temporary stalls have been set up in streets around the site.