Nottingham Castle is closing its doors for two years ahead of a £30m facelift.
The project will see new galleries, a new visitor centre, remodelled grounds and improved access to caves in the hill beneath.
The site is famous from association with Robin Hood, though little of the medieval fortification remains.
A week a of events, including an archaeological dig, storytelling and a Lego recreation of the old castle have marked the closure.
Many tourists say they are disappointed when they see the building, which was substantially demolished in the 17th Century.
The Castle Project team describe the transformation as "to reveal the diverse heritage of the last 1,000 years".
Galleries will focus on the area's history of rebellion, industry and the roots of the legendary outlaw, Robin Hood.
It has been funded by the Heritage Lottery Fund, the D2N2 business partnership, Nottingham Castle Trust and the city council.
Cal Warren, from the Castle Project, said: "It is slightly bittersweet.
"This is the end of a particular part of the castle's history and we are part of that history.
"Going forward we will be making new future history and it has been wonderful."
The castle will close at 17:00 BST on Sunday.
Nottingham City Council hope the project will attract 40,000 visitors in the first year.
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