It has a fascinating history and has been closed off to the public for years.
Many people would describe the site as a hidden gem.
And now the secret 800-year-old chamber in Neath Abbey and Gatehouse will soon be open to the public.
The undercroft — which is a recently refurbished chamber - has been inaccessible for several years due to ongoing conservation.
The access to the chamber is normally restricted to the public due to how fragile the site was.
Founded in 1130, the Abbey, which has housed Cistercian monks, boasted Tudor splendour and seen thriving industry over the centuries, has benefited from significant interpretational and structural improvements over the last decade — with critical work on the undercroft just completed.
As you head off the A465 towards the main road you will find Neath Abbey just off an industrial estate.
When you enter the site, just at the back you will find the secret chamber. Inside, you will find fascinating artefacts and impressive monastic remains from the Abbey's history.
The space in the undercroft was once a sleeping area and in medieval times it was used as a place where the monks would work during the day.
And during the Tudor period, it was the servants' hall.
Bill Zajac, Cadw historian and expert on Neath Abbey , will be the tour leader when the doors open to the public on Saturday, September 28 and Sunday, September 29 .
He describes the undercroft as "a wonderful chamber".
"The undercroft is filled with some of the finest artifacts in Neath Abbey. It's a large chamber with a beautiful vaulted roof, carried on a series of piers that are running down the centre of the room."
When asked why the undercroft is a hidden gem, Mr Zajac said that so many people don't know that it is in Neath.
He added: "It's a remarkably unknown site for a lot of people and even people in the immediate area don't know that Neath Abbey is here.
"It's special because it illustrates so many important episodes from the history of Wales, right from it's foundation in 1130 to the industrial revolution of the 18th centary."
Funded and organised by Cadw, more than 200 of Wales’s most iconic landmarks and historic attractions will welcome visitors in September as part of the Wales-wide heritage festival, Open Doors.
For more information about the free tours you can visit Cadw's webiste .
