Take a tour and discover 188 years of history at Mittagong's Fitzroy Inn

Not only that, the Fitzroy Inn was once a private boys boarding school, a traveller's inn, and a private boarding and guest house.

Originally opened in 1836, it has been fully operational for the last 188 years.

John Griffin has owned the inn since 2012 and said he was determined to preserve its legacy.

"This is our heritage," he said.

Those who visit the boutique hotel will find many original elements still intact such as fireplaces, verandas, floors, stairs, windows and walls.

These have been combined with modern comforts, and structures such as the headmaster's cottage, have been rebuilt.

Sketches and photos of the venue and how it has changed over time, historic records and artefacts can also be found.

As one steps downstairs from the atrium, they will discover the property's original kitchen, stones from Welby and those that were also used in the Berrima Gaol.

They can also find the holding cell where prisoners were transported to and from Berrima Gaol, to Parramatta Gaol.

Beams down below were also fashioned from tree trunks, which were cut by convicts, and the original oven was encased in stone and had no chimney.

Now, the downstairs section is used for functions the owner affectionately called "dungeon parties".

According to a certificate displayed in the inn from the National Trust Classfield, the building is the largest inn in the state to survive from the 1840s.

It was the first guest house open to the public, and allowed to sell liquor in NSW.

You can visit the inn for free for the historic open day and take a tour on June 1, from 9am to 3pm.

Head to Eventbrite to register, or email bookings@fitzroyinn.com.au, or call 0438 539 322.

Devonshire tea and a high tea is also available - booking is essential.