The city of Djenné (Mali) is famous for its mosque which is the world's largest adobe building. Djenné is considered to be one of the most interesting cities in Western Africa from an architectural point of view. Since 1988, Djenné is listed as a UNESCO World Heritage Site. In the 1990s, a drinking water supply network was provided by foreign development organisations. However, no facilities were provided for the disposal of wastewater, resulting in an increase of waterborne diseases. This paper describes the urban drainage problem in Djenné and discusses the systematic evaluation of possible solutions and the subsequent pilot project for the local infiltration of sullage. The infiltration of sullage proved to be an appropriate technology for solving the urban drainage problem in Djenné.