I don't know how I could possibly have forgotten this architectural gem in Oman's crown. Maybe because I have taken so many tourists here, both Muslim and Non-Muslim. Of all the Mosques in Oman, the Sultan Qaboos Grande Mosque in Athaiba area is the only one open to non-Muslims. Open in the mornings before the afternoon prayer (usually between 12-1:00 pm) so try to come before 11 pm, everyday except friday??? (Someone please correct me if I'm wrong).
For women visitors, covering the hair and skin is a must, so a headscarf is required even if you are a non-Muslim. Please try long loose clothes, with everything but the hands, face, and feet covered. For men, while it is not enforced, contrary to popular belief, Muslim men have a dress code too. Do not wear shorts shorter than knee length and it best to cover the shoulders as well out of respect. Thank you:) ;)
I remember being awed by how spacious the prayer hall was as a kid.
If you want to watch the prayers as they are led in Oman, tune in to OmanTV Arabic channel on friday between 12-1:00 ish.