Cotman's style is characterised by simplified areas of wash used with great subtlety. His watercolours were almost always done indoors but they were based on pencil sketches and observations he made outside.
Cotman first painted a view of Lyn Ogwen in 1803 after a Welsh tour. This watercolour was made much later. We know the sheet of paper was made in 1823 because of its watermark.
The artist had to rely on teaching to make a living. This watercolour is incomplete and may have been intended for a pupil to finish.