The chanting built, the drumming grew more insistent — this was the Friday evening dhikr, the rhythmic repetition of God’s name designed to bring the supplicant closer to direct contact with the almighty. A man in a leopard skin robe swung a large thurible from a rope, and smoking incense wafted into my face on the edge of the circle. As the chanting continued, a young man appeared next to me and began practicing his English. He said his name was Mahmound.

“How many wives do you have?” he asked.

“Just one,” I told him.

“Here we have two or three, four if you are a big man.” He spoke about how the Chinese had come to Sudan and were profiting, but the locals were not. He wanted to go to America. “To Miami Beach,” he said, “and Las Vegas. It is very beautiful there. Have you been? You are very lucky.”

Then another young man wearing a long robe with a green skullcap came dancing over to the edge of the circle and sprayed me and several others with something from an aerosol can. For an hour the dancing went on, the Sufi holy men chanting, “God is alive, God is alive, God is alive,” with more and more urgency, until the sun set behind the tomb and suddenly, when the music and chanting was at its most hypnotic and orgiastic, it all stopped. People tumbled to the ground, turned toward Mecca, and gathered themselves in the evening prayer.

IN the heat of the next morning we drove north, staying close to the Nile. With the city behind, the vista was broad and flat, broken only by scrawny acacia trees. Blown truck tires littered the side of the road. Occasionally a lone figure atop a camel was seen in the distance. We camped out in rolling dunes. The desert was still and the night cold.

We drove over sand to Old Dongola. From the seventh to the 14th century, this was the center of the Christian kingdom of Makuria. Little remains except some stone pillars of the Coptic Christian Church, jutting up out of the sand. Large jars, scattered and chipped, lay nearby — how many hundreds, even thousands of years old were they? No one was at the site.

For a week, we crossed and recrossed the Nile, camping in the desert or staying in simple lodgings in small villages.