Trondheim is situated where the river Nidelva meets Trondheimsfjorden with an excellent harbour and sheltered condition. The river used to be deep enough for most boats in the Middle Ages. An avalanche of mud and stones made it less navigable and partly ruined the harbour in the mid-17th century. The municipality's top elevation is the Storheia hill, 565 metres (1,854 ft) above sea level. At summer solstice, the sun rises at 03:00 and sets at 23:40, but stays just below the horizon�there is no darkness(no need for artificial lighting outdoors) from 23 May to 19 July under cloud-free conditions. At winter solstice, the sun rises at 10:00, stays very low above the horizon, and sets at 14:30
