Archaeologists are on site at the Hellfire Club in the Dublin Mountains, excavating what is believed to be an old undiscovered ancient passage tomb.
The project is set to run throughout October, uncovering the remains of the stone cairn that once formed the main mound of the tomb.
As well as the tomb, the diggers have also found a flint from people making stone tools over 5,000 years ago, some charcoal and tiny fragments of burnt bone onsite.
The destruction of the tombs is said to mark the beginning of the association of the building with the supernatural.
...and just in time for Hallowe'en.