The weekly dervish ceremony near the capital, Khartoum, is considered one of Sudan's main tourist attractions, explains BBC News website reader Mohamed El Hebeishy.
Sufism is associated with both Sunni & Shia Islam. Those who practice it are called Sufis, or Dervishes.
Every Friday dervishes gather an hour before sunset around some of the big mosques in Khartoum and Omdurman. A circle is formed and the ritual begins.