Ganzi is an off the beaten path city located at 3475m above sea level in the northwest part of the Sishuan province. It is a 6-hour minivan journey from Litang (the city displays as Garze on maps.me). Expect beautiful monasteries, stunning landscapes with snowcapped mountains and Tibetan villages.
There is a countless number of hikes from Ganzi. If you are starting to check out the Kandze Monastery on the Northern part of Ganzi, you can continue up to the Temple up-hill and then straight to the west side of the city. Do not look up for a path on maps.me since there is none mentioned. Keep walking in the mountain following the Yalong river up to somewhere in between Xiala and Nanduo. On the way back, get further deep in the mountain. You will be able to spot some terraced hillside, old Tibetan temples and abandoned cities. It should be a 20-25km hike up to 3800m above sea level. You can go much further hitchicking on the way back to Ganzi.
While there is a countless number of hikes, a day is more than enough to explore Ganzi in my opinion. Even though the mountainous scenery is amazing, it is not diverse enough to justify spending several days in Ganzi itself. On top, Ganzi is not an attractive city nor is the visual pollution of the neighbourhood urban areas. If you get plenty of time, you can explore much further west up to the Tibet border. This is supposed to be a stunning route.