The Logan Rock is an eighty-tonne granite boulder balanced on the cliffs at Treen, just east of Porthcurno — once rockable with a hand, until Lieutenant Goldsmith of the Royal Navy toppled it for a dare in 1824. He was made to put it back, at his own expense, and the Royal Navy's letter of instruction survives. It still moves a little. A fine walk from Treen, with views across to Pedn Vounder beach.