The First man from Oman who embraced Islam was The venerable Sahabi (companion of prophet Mohamed peace be upon him) Mazin Bin Gadhubah Al Sa’di. He was from Samail.
As he heard about the Prophet Hazrat Mohammad (peace be upon him), in Madina, he visited there and embraced Islam.
After Coming back to Oman, he introduced Islam to the people of Oman and built the first masjid in Oman in 6 Hijri ( About 628 AD) , it is still standing and known as Masjid Al Midhamar. It was rebuilt in 1979.
To visit here follow the location , as defined in the Map
I have visited the Holy Tomb & the Holy Masjid too in Samail.