Oil wealth has brought all the trappings of modernity to the United Arab Emirates, where clumps of soaring glass towers overlook superyacht marinas and vast shopping malls. In Abu Dhabi, even the immense Sheikh Zayed Grand Mosque – with room for over 40,000 worshippers — is just six years old. In contrast, neighboring Oman has an ancient culture and much of its architecture is traditional. The pro-Western Sultan Qaboos bin Said recently indulged his taste for classical music with a brand-new opera house, but Old Muscat has changed little in the past 400 years. Beyond Oman’s capital, travelers can still explore teeming souks and imposing mud-walled castles. Here are photo outtakes from my recent trip, which I write about extensively in the May Hideaway Report.