Fort Brockhurst in Gosport has been closed for 36 months while it was given a £100,000 makeover.
But with a massive internal refurbishment finished and a new museum room, all paid for by English Heritage, the historic building is ready for visitors again.
A lot of old items have been dusted-off and brought out of storage, so visitors can inspect history in close-up.
Among the new historic objects on display are the excavation finds from Portchester Castle and a set of chairs that belonged to William Pitt the Younger.
Pam Braddock, the fort's curator, said: 'It's great to be open again and I would love to see crowds of people flocking in.
'It is a huge fort and it would be really nice to see a lot of people coming in to look at the objects that we've got.
'Hopefully the new items and information we've got will make the fort more interesting for the public.'
The fort is initially only open on the second Friday of each month. Admission is free.
However, this may change a few months down the line, depending on how successful the newly-renovated fort is at attracting visitors.
For more information on visiting the fort, call (023) 9258 1059