Geography of Sheffield (Totley Brook passes south of Totley and meets Old Hay Brook at Needham's Dyke). The Sheaf flows northwards to join the River Don near Blonk Street Bridge in the city centre. This lower section of the River Sheaf together with the River Don, between the present Blonk Street and Lady's Bridge, formed part of the perimeter of Sheffield Castle. Porter Brook's source is just inside the Peak District National Park, to the west of the city, at Clough Hollow, also near Ringinglow. From here it flows eastward to meet the Sheaf, at a point now located underneath Sheffield Midland Station.
Sheffield There are six areas within the city that are designated as sites of special scientific interest. The present city boundaries were set in 1974 (with slight modification in 1994), when the former county borough of Sheffield merged with Stocksbridge Urban District and two parishes from the Wortley Rural District. This area includes a significant part of the countryside surrounding the main urban region. Roughly a third of Sheffield lies in the Peak District National Park. No other English city had parts of a national park within its boundary, until the creation in March 2010 of the South Downs National Park,