The sea depth at the North Pole has been measured at 4,261 m (13,980 ft) by the Russian Mir submersible in 2007[3] and at 4,087 m (13,410 ft) by USS Nautilus in 1958.[4][5] The nearest land is usually said to be Kaffeklubben Island, off the northern coast of Greenland about 700 km (430 mi) away, though some perhaps non-permanent gravel banks lie slightly closer. The nearest permanently inhabited place is Alert in the Qikiqtaaluk Region, Nunavut, Canada, which is located 817 km (508 mi) from the Pole.