Enquiries to the estate had got me nowhere and things were sketchy online, so as we were in Skibbereen anyway, we drove up to the front gate of the Liss Ard estate, not expecting much at all really. But the automatic gate slowly opened, so in we went. Inside all was empty and quiet except for the sounds of birds singing. We explored some of the acres of lovely woodland, not seeing a soul, then went up to the main house.

In the end it wasn’t so mysterious at all. In the house, I was greeted by the pleasant receptionist who handed me a card with four numbers on (okay, it was a little mysterious). This was the combination for the padlock.

We walked along a high wall then came across a large stone entranceway. This led down some stairs and along a path through a field. We turned into some woods, and there was a large grass mound with a metal gate at the base, with a concrete tunnel running through the mound.

This was all in the name of art for we were finally at the entrance to James Turrell’s Sky Garden. We unlocked the padlock and walked through the dark tunnel to emerge into a wide grassy crater. In the middle was what looked like a stone tomb or sacrificial altar. In situations like this, the film The Wicker Man always springs to mind.

The sky garden is situated on what is known as an ancient ring fort, which actually wouldn’t have been a fort at all but rather a peaceful farmstead. There would have had a tunnel too, known as a souterrain (possibly similar to the Cornish fogou). The Turrell sculpture evokes Ireland’s ancient past.

Though the manor was built in 1853, Liss Ard Estate was founded in 1990 by two art dealers, who commissioned Turrell to create the Sky Garden in 1992. It was since taken over by another art dealer who hosted concerts on the estate in the 1990s and 2000s. Nowadays the venue can be hired for weddings and various events, and provides everything from yoga retreats to night kayaking.

I lay down on the alter and looked up; I could see the sky and in my peripheral vision could just make out the green rim of the crater bowl. There was complete silence and tranquility. The stone alter was a bit hard. Says James Turrell, “The most important thing is that inside turns into outside and the other way around, in the sense that relationships between the Irish landscape and the Irish sky changes”. I don’t know about that, but it was pretty cool.

• There is also a smaller scale James Turrell installation at the Tremenheere Sculpture Gardens near Penzance in Cornwall.