The only way to get into core Bhaktapur city is to need buy a ticket at the main gate along other entrance counter around Bhaktapur. For foreigners, it costs NRP 1500. (NPR 500 if you are from a SAARC country).
This entry ticket will be extended for up to one week without charge if you produce your passport.
A licensed local guide will be waiting for you at the ticket booth to help you explore the ancient heritage town. NPR 200/300 determines the guide charge (or more basis on the number of people in the group).
You do not have to pay the ticket price if you are staying in Bhaktapur for the night. When any ticket counter personnel asks to see your entrance ticket while you’re out and about in the city, you’ll need to display it. If you can’t present your ticket, you’ll have to buy another one or you’ll be barred from entering the city.