During the gold rush between the late 1870's and 1910's many mine shafts were constructed on Towers Hill.
To store military assets away from the coast, Towers Hill shafts were turned into ammunition storage bunkers during World War 2.
There are displays, a walkway and undercover seating here.
Cachers may need to out wait any muggles present. You are searching for a undersized thematic container, with a magnet at one end. It can be found without going over the railing, at a stretch. There is a very small unactivated trackable for FTF -which was Phoenix Ferals. Bring a pen.
July 2019 edit - The council has installed an interactive display at this location, which is accessed via a smart phone app - more information here: Towers Hill augmented reality app.