The Sheela-na-gig figure is one of only two known in Wales

Juilette Paterson, the wife of Powys' former county surveyor, known as Colonel Paterson, left �453,000 to Radnorshire Museum at Llandrindod Wells.

Mrs Paterson's husband helped to set up the museum, and her gift will enable it to start a complete revamp.

Many items in storage will now go on show in a new first floor gallery.

It will also allow existing items on display, including one of the internationally renowned Sheela-na-gig figures dating back to the Dark Ages to be kept in a controlled environment that befits its age and importance.

This development will provide a huge boost for the local community because this museum has been in the doldrums Will Adams, joint curator

The project will also improve the physical access to the museum's collection on both ground and first floors - including a lift to improve access for the disabled - and allow it to develop an education and outreach project of events and activities.

"This development will provide a huge boost for the local community because this museum has been in the doldrums," said the museum's joint curator, Will Adams.

Roman fort

"Colonel Paterson was heavily involved in founding the museum and many artefacts from his own collection are now stored here.

"We will be able to convert our present storage area into a display gallery which means more artefacts from our vast collections can be put on display."

This will include a collection of remains from the Roman fort at Castell Collen, near Llandrindod Wells.

"We would also like to display artefacts found at Walton Basin, near Presteigne where neolithic wooden palisades similar to the stones at Stonehenge stood," said Mr Adams.

Officials say the bequest will benefit Llandrindod Wells

"This 50-acre enclosure was the largest of its kind in Britain and it is believed to be the largest in Europe," he added.

"We have pot fragments and flint finds from Walton Basin and we would like to provide an interpretation of this site to educate people about this important site."

The Sheela-na-gig figure housed at the Radnorshire Museum is one of only two known in Wales.

"It is a really well preserved example having been buried underneath the threshold of the old parish church for many years," said Mr Adams.

The plans for the development of Radnorshire Museum are on display at its Temple Gardens base. The museum has also applied for lottery funding.