The Nor Loch, also known as the Nor' Loch and the North Loch, was a man-made loch formerly in Edinburgh, Scotland, in the area now occupied by Princes Street Gardens and Waverley station which lie between the Royal Mile and Princes Street. Geological formation The depression, along with the parallel one now occupied by the Cowgate, was formed by glacial erosion during the last Ice Age, when the icepack was forced to divide by the volcanic plug now known as Castle Rock. Early history A marsh formed in the hollow and was part of the natural defence of the Old Town of Edinburgh. In 1460 King James III ordered the hollow to be flooded in order to complete the defences of the town and Edinburgh Castle. The loch was formed by creating an earthen dam to block the progress of the Tummel Burn, a stream that ran along the foot of the north side of the castle rock. The water level was controlled by a sluice in the dam which was at the foot of Halkerston's Wynd. Because the Old Town was built on a steep ridge, it expanded on an east-west axis, eastwards from the castle; expansion northward, as would happen with the later New Town, was extremely difficult at this point. The Nor Loch was thus a hindrance to both invaders and town growth. In the winter of 1571, as part of a plan to end the "Lang Siege", the Earl of Morton explained that, "One side of the town is 'unwallit', and the frost may give occasion to assault it that way with far less difficulty than otherwise", suggesting that the requested English army could cross the frozen Loch. In 1603, King James VI gave the Town Council title to the land, pools and marshes of the loch. Middle Ages to 19th century As the Old Town became ever more crowded during the Middle Ages, the Nor Loch became similarly polluted, by sewage, household waste, and general detritus thrown down the hillside. The loch was never used as drinking water but there were wells beside it (see below). The Nor Loch fulfilled a variety of other roles during this period including: Defence: Scotland, and particularly Edinburgh, suffered frequent English invasions during the period of intermittent Anglo-Scottish wars from the 13th to 16th centuries. Suicides: The Nor Loch was a common spot for suicide attempts. Crime: The loch