Chichester's Roman baths have been uncovered for the first time in 17 years.
The baths are to be the main attraction of the new £6.9m District Museum planned for the Tower Street site.
On Tuesday, archaeologists began exploratory work of the ancient remains currently buried underneath a car park.
Archaeology South East closed the car park for a four-week period while they assess the site's condition.
Project manager Diccon Hart hopes the new exploration will bring the previous findings up to date.
He said: "We are excited to be working on the site. It is one of the more significant sites in the Chichester area. We wish to fully and accurately locate the previous findings using modern equipment to assess any changes to 17 years ago."
First discovered in the 1970s by Chichester archaeologist Alec Down and a team of volunteers, the baths are due to undergo a full re-excavation to be on permanent display as the centrepiece of the new museum.
Cllr Nick Thomas, responsible for culture and sport, said: "Although access to the car park will be closed, members of the public will be able to see the work in progress from the footpaths around the edge of the car park, giving them a glimpse of what they can expect to see at the proposed museum."
Cllr Thomas believes that the Roman baths will bring something extra-special to the museum.
He said: "Having these remains is a great bonus. The whole team is looking forward to seeing the remains and checking their condition so we can safeguard them in the new building."
The archaeologists will also examine areas underneath a proposed housing development on the site.
"This is to ensure the building design will not damage any archaeological remains, and allow them to be preserved for the future," said a district council spokesman.
"It will also reduce the risk of any new archaeological discoveries during the main construction period which could cause delays and extra costs."
Following the excavations, the lower, larger part of the car park will be re-opened, but to protect the remains, the upper area will stay closed.