While many of the old palace structures contained within the courtyard of Hanuman Dhoka are closed to the public, the square itself is well worth a visit. Check out the Hanuman statue as well as the old audience chamber of the Malla royalty and the intricately worked gate through which you enter the courtyard area.
Entrance into Hanuman Dhoka is included in the Durbar Square fee. Set aside at least a half-hour to explore the courtyards and ancient temples of the complex, but remember that photography is only permitted in the outdoor courtyards. Look for an inscription in the wall of the palace; it's written in 15 different languages and, according to local legend, if someone successfully deciphers the inscription in every language, milk will begin flowing out of a nearby spout.