Budhanilkantha is located in the north most corner of Kathmandu valley and on the foot of Shivapuri Nagarjun national park. Kathmandu and Nepal is blessed with sacred sites scattered all around the nation. This one in Kathmandu valley and out of tourist radius as well as sightseeing circuit.
The temple houses a statue of Vishnu in the form of Narayan. The reclining statue of Narayan was carved out of a single black boulder and was carried in the place that it resides in the present day in 6-7 AD. This temple is mostly flocked by the locals and it is one beautiful sight to observe if you are a foreigner.
Very close to the temple is also the Hare rama hare Krishna temple opened by ISKCON. The Budhanilkantha is open only for the followers of Hindu whereas the ISKCON temple can be visited by people of any and all religion.