Koolen was always inspired by what the Limburg life typified in the period up to the sixties: processions, country and village life on land. He was concerned about the fate of the small farmer on leased land who was threatened in his existence by advancing urbanization.
Marian Procession, oil on canvas
Sanctuary procession, oil on canvas
One last farmer and the city,oil on canvas
Farmers servant and his wife looking for work, oil on canvas
Some friends paid their last repects to Mr. Knols, the forester of Terworm, gouache on hardboard