Mildenhall Museum’s new look was unveiled on Saturday, before it closed again to allow the final improvements to be fitted.
When work is completed Mildenhall Museum will have the space, conditions and security to house the Anglo Saxon Lakenheath warrior and horse found at RAF Lakenheath.
More than 100 people attended the open day where the extension, including a new community area was unveiled.
Stephanie Palmer, chairman of trustees, said: “We are thrilled to bits.
“The word Tardis was used several times.”
On Monday the museum was handed over for six of its eight rooms to be refitted.
The museum will begin a slow opening as works are completed culminating in a celebratory event when the Lakenheath warrier goes on display.
The extension will also allow the museum to put items previously kept in storage on display and invite travelling exhibitions to the town.
The community space will be used by visiting schools and community groups looking for somewhere to stage events or meetings.
All of the exhibits on display at the museum are linked to Mildenhall and the surrounding villages.
They range from fossils to modern items and will include a hoard of Roman coins recently purchased by the museum.
The work has been funded Lottery Funding, Suffolk County Council, Forest Heath District Council, and the Museum Society.