Driving in over a land border?

Oman has land crossings with the UAE and with Saudi Arabia. Whichever you use, you need your passport, the car's registration, and insurance that explicitly covers Oman; a rental also needs a no-objection letter from the hire company. The UAE crossings are the busiest and the best organised. Reaching Musandam by road from Muscat means transiting the UAE either way. Opening hours and rules change, so check the day before you drive.