Complex sentence: Hiking as an activity started in its true sense of work circa 1930, the year in which a group of friends climbed the Đeravica mountain in Peć, the first time that a peak in Kosovo was climbed.
Split into simpler sentences: Hiking as an activity started in its true sense circa 1930, the year in which a group of friends climbed the Gjeravica mountain in Peć. This was the first time that a peak in Kosovo was climbed.