The decision to construct a New Town was taken by the city fathers, after overcrowding inside the Old Town city walls reached breaking point and to prevent an exodus of wealthy citizens from the city to London. The Age of Enlightenment had arrived in Edinburgh, and the outdated city fabric did not suit the professional and merchant classes who lived there. Lord Provost George Drummond succeeded in extending the boundary of the Royal Burgh to encompass the fields to the north of the Nor Loch, the heavily polluted body of water which occupied the valley immediately north of the city. A scheme to drain the Loch was put into action, although the process was not fully completed until 1817. Crossing points were built to access the new land; the North Bridge in 1772, and the Earthen Mound, which began as a tip for material excavated during construction of the New Town. The Mound, as it is known today, reached its present proportions in the 1830s.