Muscat is the Gulf's finest city break and the one that feels most like a genuine place rather than a constructed experience — an ancient harbour capital of low white buildings under the Al Hajar Mountains, with the finest Grand Mosque in the Arabian Peninsula (the Sultan Qaboos Grand Mosque, completed 2001), the most atmospheric traditional souq in the region (the Mutrah Souq, on a corniche that has been a trading waterfront for 2,000 years), and a warmth of hospitality that is the defining characteristic of Oman. The sultanate is consistently rated among the safest and most welcoming countries in the world for international visitors. The dramatic wadis, mountains and desert of Oman's interior are accessible within an hour.
From London Heathrow it's about 7.5 hours — Oman Air flies direct from Heathrow; connections via Dubai or Doha are available from most UK regional airports. Muscat International Airport is 35km from the Mutrah waterfront (taxi, 35 minutes, 15–20 OMR or app-based Mwasalat taxis). Go from October to April: temperatures are perfect (24–30°C), the outdoor life is at its finest and the mountain and wadi excursions are comfortable. May to September is extremely hot (40°C+) and the outdoor experience is very limited.