Pen Park Hole is a large cavern situated underground, at the edge of Filton Golf Course.

Here they found what they thought was a rich mine "an abundance of strange places, the flooring being a kind of a white stone, enamelled with lead-ore, and the pendant rocks were glazed with saltpetre, which distilled upon them from above, and which time had petrified."

After a few hours they ascended to the surface, but the unfortunate Captain Sturmy suffered from a severe headache for four days, developed a fever and died.

[3] On 17 March 1775 Reverend Thomas Newnam of Redcliffe Church fell to his death while attempting to plumb the depth when the tree branch onto which he was holding broke.

[5] The cave entrance is in a residential area and is protected by a steel plate for safety reasons.