Located 10 kilometres south-west of Braidwood along Majors Creek Road, it was built by entrepreneur Charles Dransfield who made his fortune growing wheat and selling gold leases in the 1850s.

But prolonged drought conditions devastated the regular wheat supplies of the then 1200-acre property and the mill was closed for business, its steam engine and fittings dismantled and sold to make ends meet.

Having changed hands several times between extended family in the intervening century, the mill stood exposed to the elements until current owners Antony Davies and Andrew Gow made it their mission to rescue it.

The historic property, now known as Millpond Farm, will be open to the public on Saturday and Sunday as part of the expanded Braidwood Open Gardens, an annual event that showcases local gardens, homesteads and properties of note while raising funds for the town's not-for-profit preschool.

Today the mill is the impressive centrepiece of Millpond Farm, having been faithfully restored to its former glory by the couple who spent years researching the mill, the property's farmhouse and outbuildings before painstakingly restoring each to their original state.

Their attention to detail means it's easy to assume the impressive house, 1840s timber wagon barn and four-storey mill have all been immaculately maintained since Dransfield first set about growing his empire.

But Andrew and Antony – an antiques dealer and valuer whose passions include restoring vintage cars and horse-drawn vehicles – say it has been a labour of love.

Eight years of hard graft have gone into replicating every detail, from the Gothic-revival bargeboards on the farmhouse to the mill's timber sash windows, which the couple had made by Amish craftsmen in Pennsylvania to match the only one left intact.

While Antony admits there is still much to be completed, he says the "work in progress" has come a long way since 2008.

Antony and Andrew laugh when they recall the original state of the house. "It was so cold in winter that if you left water in the sink overnight, it would be frozen by the morning," Andrew remembers.

Not to mention the family of possums who called the roof home. "We kept catching and relocating them, painting their tails to make sure none were returning, and couldn't believe it when we got to 26!"

After restoring the mill, the couple opened Wheatfield Gallery on the lower floor and each year the farm runs a series of traditional craft courses.

Future plans for the building include a cafe and five luxury farm-stay apartments on the upper floors that will be available as artist-in-residence spaces.

The couple are working with friends to rehabilitate a 25-acre wetland on the property and planting has begun to create an arboretum with 25,000 specimens. A bird-watching trail with views to the Tallaganda and Budawang ranges is under construction, allowing visitors to view migratory birds, platypus and wallabies.

Antony and Andrew are committed animal lovers and their domesticated and wild menagerie plays a large part of Millpond Farm's charm. Their flock of fine-wool alpacas graze contentedly in the front paddock and their fur family includes sheep, carriage horses, goats, an elderly lama and two dogs – including an ancient wolfhound – who enjoy a trip into Braidwood in one of Antony's vintage cars.

Visitors this weekend will be able to wander a section of the property and for a gold coin donation, view an art exhibition on the lower floor of the mill. It will include a preview of a vintage film poster collection, part of an exhibition beginning in November.

The donation will also grant access to the stables and wagon barn, where Antony houses his collection of horse-drawn vehicles and vintage cars, including a 1925 MG, 1929 Sunbeam and 1915 Republic truck.

On Saturday, members of Braidwood's two vintage car clubs will display some of their early vehicles and on both days, Landcare will host children's activities and talks in the mill by industry experts on the Scarlet Robin Project, aimed at protecting the habitat of eight woodland birds in south-east NSW.

Gardens open over the weekend include Green Farm and Tudor Valley (Reidsdale), Linden and Durham Hall (Jembaicumbene, near Millpond Farm), Deua Tin Huts (Krawarree), Wynlen House Slow Food Farm and Bedervale Homestead (Braidwood).

Each property will be open 10am-4pm both days. Entry is $5 per property, under 18s free.

For more information, visit www.braidwoodgardens.com.au