Hindu and Vaishnav devotees gather infront of Krishna Mandir at Patan Durbar Square on the eve of Krishnastami and stay in vigil until midnight. The celebration proceeds with incantations and lighting of traditional oil-lamps. During the day, a religious procession is organised through the city and traditional music is played as it gets along.
The temple itself is a historical monument, as is the Patan Durbar Square (recognised by UNESCO as a World Heritage Site. The site can be visited at any time of the year, but choosing this day would allow you to witness more than structures, but also the centuries old culture preserved till date. Do not forget your camera!