The River Guadix, a sub-tributary of the Guadiana Menor, which flows through the town of the same name must lay claim to world’s most tautological geographical name.

Wikipedia claims in tautological place names:

Río Guadix, Spain (The River River River – Río is “river” in Spanish, Guad < w?d? is “river” in Arabic and Ix is “river” in Phoenician)