The 55 Window Palace was built in 1754 and is located in Bhaktapur Durbar square as one of its main attractions. At one end it the National Museum of Art while at the other you can enter through The Golden Gate.
Once inside the 55 Window Palace non-Hindu's cannot go further into the inner palace. However you may visit the than the royal water tank Naga Pokhari
Read more in this guide to the 55 Window Palace.