It is known as 'the white city' for its white-washed brick houses in the centre of town.

], the region of Thorn was a swamp nearby the Roman road between Maastricht and Nijmegen.

Previously the abbess and the chapter were endowed with religious tasks but, since the 12th century, they served secular matters and formed the government of a truly sovereign miniature principality, a smaller independent state in the German Holy Roman Empire, approximately 250 x 250 metres.

Besides Thorn, Ittervoort, Grathem, Baexem, Stramproy, Ell, Haler and Molenbeersel belonged to this principality.

After the French invasion in the winter of 1794–95 and the formal abolition in 1797 made an end to the existence of the abbey and the principality of Thorn; Thorn was first part of the department of Meuse-Inférieure, and after the Vienna Congress it became a municipality of the United Kingdom of the Netherlands.