Rabat's Royal Palace is still a working royal compound, so the attraction is the approach rather than the interior. The broad avenues, formal gates, guards, and long palace walls give a good sense of the city's role as Morocco's political capital.
Visitors are usually limited to walking between the outer entrances and looking in from the permitted areas. Bring your passport, behave respectfully around the guards, and treat it as a short architectural stop rather than a palace tour.