Tourism, and associated commercial activities have led to physical damage and discolouration of the famous white travertine terraces at Pamukkale, a World Heritage Site. To mitigate these environmental impacts, scientific studies were started in 1993 by UKAM and the Ministry of Culture. These show that an aquifer within Paleozoic marbles and Mesozoic limestones, with a capacity of delivering 510 l/s, feeds the hot springs associated with the terraces. The discolouration results from algae, whose growth is enhanced by the use of open channels to convey the water to swimming pools, and by subsequent discharge of the water onto the terraces. Leakage of effluent from septic tanks has encouraged algal growth near the base of the terraces. To protect the terraces and enhance travertine deposition, covered concrete channels have been built to reduce algal growth and a road across the terraces closed. Recommendations for additional protective measures include reduction in commercial tourist activities, removal of septic tanks and swimming pools, prohibition of walking on the terraces, and the creation of special regulation and protected zones. (C) 2000 CNR. Published by Elsevier Science Ltd. All rights reserved.