How to make the most out of 7 hours in Muscat

Dear Muscat Community,

We will be in Muscat on Feb. 3 for approx. 7 hours and would appreciate your advice on how to make the most of these 7 hours in Muscat. What is the absolute must see? How to move around best? Is it advisable to have a private guide? Can you recommend someone? We are a group of four people. It would be great to hear back from you. Thanks a lot!

Cheers, Ute