 By 1822 he had become known as a painter of architectural subjects, with particular focus on the representation of medieval German churches, in which architectural details were first drawn in pen, then glazed over with oil paint.Favorite subjects included the cathedrals of Magdeburg and Halberstadt, where he lived from 1828.After 1838 Hasenpflug concentrated on paintings of snow-covered ruins that combined factual observation with fantasy.