When the Grotto was discovered, it was big surprise - no one seemed to know of its existence, it wasn't on any map & there were no local tales of a hidden place covered in shells. Its age can't be determined by carbon dating as the shells are covered in carbon from the gas lamps used to light it before electricity & its use can't be determined either. It may have been a pagan temple, a meeting place for a secret sect, a smuggler's hidey-hole, or even something to do with the Knights Templar, but the most recent discoveries point to a sun temple. The sun enters the dome - which extends to ground level & has a small circular opening - just before the Spring Equinox & forms an alignment at noon on the Summer Solstice with what might have been part of an altar & it disappears just after the Autumn Equinox, which indicates the fertile season.
Looking up through the dome to outside.
There was some belief that the grotto may have been a rich man's folly - there are loads of follies around, but they're on top of the ground, not hidden away underground. Follies are also normally associated with large country estates, but this grotto is on what had always been farmland.
Looking back towards the stairway down into the grotto. This is a subterannean structure, with a fairly steep sloped walk way into the actual grotto itself. To visit the grotto, you enter through the shop & the stairs down are at the back by the counter. When I was a kid, it was a poky, dark, tiny little shop, but when I went 4 years ago, the then new owner had opened it right up & had a lovely little cafe area & all sorts of grotto associated items for sale.
At one time, it was thought that the grotto was built in the 1700s, but that thought was dismissed because it seemed impossible that no one in the town knew of it when it was discovered in 1835 . It would have taken a large workforce & a lot of time & work to excavate it & stick over 4½ million shells on the walls. Keeping a project like that secret would have been nigh on impossible.
This is thought to be part of the altar. The shells used on the walls are mostly those found locally - oyster, cockles, mussels & whelks. They're glued on with a type of fish paste glue that also has traces of volcanic elements. No one has yet been able to identify exactly what it's made from, but it's pretty good !! :o)
The shells form patterns that may point to fertility, the circle of life etc.
If you look closely, you can see gods & goddesses, phalluses, flowers, stars, trees of life, that sort of thing, so it seems that the thought behind it being a sun temple may be the right one. However, nothing is 100% certain & I think the research is ongoing.
The passageway is approx. 70 feet long & 8 feet high. At the end of it is a rectangular shaped room, about 15 feet by 20 feet, where the altar is. Roughly in the middle, the passageway splits into 2 so that you can go around a circular column called the rotunda.
Almost every square inch of wall & ceiling is covered with shells, but unfortunately, in places, they've come off. Whether that's due to age, atmospheric conditions or visitors touching them is unclear.
The arched doorway, very reminiscent of churches & catherdrals, so maybe the grotto was a religious meeting place. Like Stonehenge, I don't think we'll ever know for sure exactly what the grotto was built for, but it really is worth a visit.