It stands on a prominent ridge 700 ft (213 m) above sea level, within the boundary of Pontypool Park, Torfaen in south Wales.

During the early 19th century, Capel Hanbury Leigh (6 Oct 1776 - 28 Sep 1861) undertook renovations of the family house and park's grounds and it is thought that his wife Molly Ann (married 14 Apr 1797, she was the widow of Sir Robert Humphrey Mackworth (died 1794))[3] was responsible for the interior shell decoration.

The grotto is constructed of local red Pennant sandstone and conical stone tiled with a fan vaulted roof (with six fans rising from six pillars) and the supporting pillars and ceiling are covered with thousands of shells interspersed with minerals and real stalactites removed from caves in the local area.

Initial reviews of the cost of renovating the property were very high and the local council sought external financial assistance.

Although some minor restoration to the roof was undertaken in January 1992, the grotto continued to suffer and the external walls were quickly becoming a major issue.

It was during 1992 and 1993 that the intervention of the Welsh Heritage Authority, Cadw, and the European Regional Development Fund, that enough donations were secured to cover complete restoration of the building.

In 1995 a campaign was begun to raise funds to match the local council's resources to restore to former glories the interior of the grotto.

The rustic chairs were restored by piecing in new segments which were missing, repairing broken sections, and scraping back layers of modern paint.