In this June 27, 2006, file photo U.S. military guards walk within Camp Delta at the Guantanamo Bay U.S. Naval Base, Cuba. The U.S. announced the transfer of four detainees from Guantanamo to Oman; one will go to Estonia. Brennan Linsley/AP hide caption

itoggle caption Brennan Linsley/AP

The Jewel of Muscat, a replica of a ninth century Omani trading ship, sails into the harbor of Galle, Sri Lanka, in 2010. The ship was built in a traditional manner that uses coconut fibers (but no nails) to hold the ship together. The ship followed old routes used by Arab traders. Lakruwan Wanniarachchi/AFP/Getty Images hide caption

itoggle caption Lakruwan Wanniarachchi/AFP/Getty Images

Sultan Qaboos bin Said, 73, salutes during a military parade in the capital Muscat on Oman's national day in November 2013. Qaboos, who has ruled for 44 years, has maintained friendly relations with everyone from the U.S. to Iran. However, he has been abroad for months receiving treatment for an undisclosed illness. Mohammed Mahjoub/AFP/Getty hide caption

itoggle caption Mohammed Mahjoub/AFP/Getty