Remains of the 12th Century Gloucester Castle building were unearthed in 2015 during an archaeological dig.
Its exact location had remained a mystery for more than 200 years because the site was in the grounds of the city's jail, which closed in 2013.
The keep's location is to be shown within a paved area of a new residential and business development.
Revised plans for apartments and offices have gone on display in a public consultation at the site, after the original plans were altered to take account of the archaeological discoveries.
The former prison was originally built in 1791 over the levelled remains of Gloucester Castle, the keep of which had been used as the county jail since the 15th Century.
The location of a Norman castle keep is to be depicted in a new development at a former prison site.