Muscat is likely the start and finish of your Oman road trip adventure. While I focused on the historic and natural attractions elsewhere in the country, I still allocated one full day for sightseeing in the city to match up with my flight time.
Sprawled out across a wide swath of coastline, driving is a must to get around the city. Keep the car until you reach the airport for your flight out. Highways here do get congested even though the city is only home to just over 1.2 million.
Muscat was a major Arabian Sea port by the end of the 15th century, and the Portuguese came invading in 1507, holding on for over a century. The locals kicked them out in 1650 and repelled subsequent Persian invasions.
Spend at least half your day exploring the historic area in Mutrah, including its souks, although that part is too touristy especially when the cruise ships are in town. Make some time in the morning for the sultan's mosque in the west side of town as well as a tour of the opera house. You can visit the modern malls at night after the attractions close.