"Booval House" at Cothill Road, the oldest two-storey home in Ipswich, would likely be worth $10 to $15 million in Brisbane but will sell for a fraction of that, its marketing agent says.

Aidan Wales of Ray White Ipswich says the property, an Ipswich landmark, reminds him of Vaucluse House in Sydney with its grand architecture and stately grounds.

"Of course, this isn't Sydney and the prices here are very different. Even in Brisbane, something like this would be worth $10 to $15 million," he says.

"I can't actually think of a house in Brisbane that rivals it when you take into account the size, the history and the land size."

The property is being auctioned, so by law Mr Wales can't name any price expectations. He says while it's hard to find comparable recent sales because of Booval House's unique heritage, it's probably not as expensive as some might expect.

"We do find sometimes with these unique properties that buyers just assume they can't afford it," he says.

"They might think a property is going to go for $4 million when it in fact goes for $2 million or even $1.5 million.

• Related: The most beautiful country Queenslanders
• Related: Renovating Queenslanders
• Related: Brisbane's 'most beautiful Queenslander'

"What I can tell you that two nice homes nearby sold for $800,000 to $1,000,000, although they weren't a patch on Booval House's land size and they were not even National Trust properties."

Ipswich is renowned for its proliferation of historic Queenslanders but Booval House would have to be one of the most impressive.

Set on an immaculately landscaped 4818 square metres of private grounds, the original house was built between 1857 and 1859 and stands as a rare Queensland example of colonial Georgian architecture.

Originally owned by a prominent Ipswich banker, the house passed through two other families before the Sisters of Mercy purchased it in 1931 and turned it into a Catholic convent.

Its current owners, John and Helen Jackson, bought the property 20 years ago and spent the best part of two decades painstakingly restoring it back to its now glorious state.

Their conservation work won them the National Trust of Queensland's highest award ??? the John Herbert Memorial Award for Excellence in Conservation.

Apart from the five-bedroom, three-bathroom Booval House, the property also includes the two-storey east wing annexe, a garage/workroom wing, sulky shed and lean-to, fernery, orchid house and a leafy summer house.

The Special Uses (SU) 80 zoning adds opportunity to use the grounds commercially with some potential uses being a function centre, catering caf??, accommodation (Airbnb), religious/musical/education centre, professional/medical offices to name a few.

The auction is scheduled to take place at Ray White Corporate, Level 26, 111 Eagle Street, Brisbane, this Friday August 25 at 10.30am.