I have 2 nights and 1 day
Go to the Muttrah Souk. You will probably get lost but that's all part of the fun! Then maybe head over to see Al Alam Palace and/or check out views from Kalbuh Park on the way. Good food is surprisingly hard to find in Muscat IMO but I like Mumtaz Mahal Restaurant for Indian and usually one of the Lebanese restaurants are a good choice. The Omani coast is incredibly beautiful and worth a boat/snorkeling tour if you can do it.
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