The area in the vicinity of the Belvedere Tower is home to one of the largest collections of glacier mills in Europe. These circular cavities in the rock, which may be several metres deep, were formed during the retreat of the mighty Inn Glacier after the last ice age, and were discovered in 1884 during construction of the Belvedere Castle. Altogether, 36 glacier mills of various sizes can be seen in the area north-west of Maloja. An attractive circular trail leads past these geological wonders, and takes about an hour to walk. The glacier mills by the Belvedere Tower form part of a nature reserve that belongs to the Swiss conservation organisation Pro Natura.