Oldham 's topography is characterised by its rugged , elevated Pennine terrain . It have an area of 6 @.@ 91 square miles ( 17 @.@ 90 km2 ) . The geology of Oldham is represented by the Millstone Grit and Coal Measures series of rocks . The River Beal , flowing northwards , form the boundary between Oldham on one side and Royton and Shaw and Crompton on the other .