Ancient Ghana derived power and wealth from gold and the introduction of the camel during the Trans-Saharan trade increased the quantity of goods that were transported. Majority of the knowledge of Ghana comes from the Arab writers. Al-Hamdani, for example, describes Ghana as having the richest gold mines on earth. These mines were situated at Bambuk, on the upper Senegal river. The Soninke people also sold slaves, salt and copper in exchange for textiles, beads and finished goods. They built their capital city, Kumbi Saleh, right on the edge of the Sahara and the city quickly became the most dynamic and important southern terminus of the Saharan trade routes. Kumbi Saleh became the focus of all trade, with a systematic form of taxation. Later on Audaghust became another commercial centre. The wealth of ancient Ghana is mythically explained in the tale of Bida, the black snake. This snake demanded an annual sacrifice in return for guaranteeing prosperity in the Kingdom, therefore each year a virgin was offered up for sacrifice, until one year, the fiancé (Mamadou Sarolle) of the intended victim rescued her. Feeling cheated of his sacrifice, Bida took his revenge on the region, a terrible drought took a hold of Ghana and gold mining began to decline. There is evidence found by archaeologists that confirms elements of the story, showing that until the 12th Century, sheep, cows and even goats were abundant in the region. The route taken by traders of the Maghreb to Ghana started in North Africa in Tahert, coming down through Sjilmasa in Southern Morocco. From there the trail went south and inland, running parallel with the coast, then round to the south-east through Awdaghust and ending up in Kumbi Saleh - the royal town of Ancient Ghana. Inevitably the traders brought Islam with them. The Islamic community at Kumbi Saleh remained a separate community quite a distance away from the King's palace. It had its own mosques and schools, but the King retained traditional beliefs. He drew on the bookkeeping and literary skills of Muslim scholars to help run the administration of the territory. The state of Takrur to the west had already adopted Islam as its official religion and established closer trading ties with North Africa. There were numerous reasons for the decline of Ghana. The King lost his trading monopoly, at the same time drought began and had a long-term effect on the land and its ability to sustain cattle and cultivation. Within the Arab tradition, there is the knowledge that the Almoravid Muslims came from North Africa and invaded Ghana. Other interpretations are that the Almoravid influence was gradual and did not involve any form of military takeover. In the 11th and 12th Century, new gold fields began to be mined at Bure (modern Guinea) out of commercial Ghana and new trade routes were opening up further east. Ghana then became the target of attacks by the Sosso ruler, Sumanguru. From this conflict in 1235 came the Malinke people under a new dynamic ruler, Sundiata Keita and soon became eclipsed by the Mali Empire of Sundiata.