In a depression between the monument and the castle are the remains of the "Smugglers' Cave". It was blocked with rocks by the council in the 1980s to stop children entering. The tunnel is rumoured to extend from the top of the carn into Redruth town, but it is probably an abandoned mine working. It may have been confused with another tunnel from the castle to St Uny's church which was blocked for safety reasons around 1970 by the castle owners.