Nagarjun, also known as the Rani Ban (Queen's Forest), which is home to pheasants, deer, monkeys and a couple of military posts. It is one of the last significant areas of untouched forest in the valley. There are 19 climbing routes from grade 4 to 7b overhang climbing including multi pitches of 65 meters to single pitches at 12 meters. The cliff is broken up into 4 separate faces. Most of the climbing is slightly slabby to vertical, and the routes would be considered moderate difficulty.
Nagarjun Forest Reserve is in northwest Kathmandu, just outside of the ring road. The main entrance to the reserve, Phulbari gate, is about 2km north of Balaju, which is about 5 kms from the center of the city. There is a fee to enter the reserve and like everything in Nepal, foreigners pay a premium. Foreigners pay 250 NR, whereas locals pay 10 NR. There is also a charge to bring in a car/motorcycle/bicycle 100/30/10NR. You will have to pay and register with the attendant before you are allowed to enter the park. The park is open 7am-7pm during summer and 7am-5pm in winter.
In addition to rock climbing, many people visit the park to hike to the summit for the great views of the valley. A winding unpaved road and a much more direct footpath lead to the summit (2095m), which is a popular Buddhist pilgrimage site (the reserve is named after the Buddhist saint Nagarjuna). There's a small shrine at the summit to Padmasambhava (Guru Rinpoche in Tibetan) and a viewing tower offers one of the valley's widest mountain panoramas, stretching on a clear day all the way from the Annapurnas to Langtang Lirung, via Machhapuchhare, Manaslu and the Ganesh Himal (a plaque at the bottom of the tower identifies all the peaks). There are also grand views of Kathmandu and its valley laid at your feet to the south, assuming you can see through the smog and pollution. It's possible to make an enjoyable two-hour cardio-hike up to the summit from near the main gate.