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The Cevizlik water tunnel is located under the Cevizlik Mosque in the Yolaltı District of the Kozluk district of Batman province. Yolaltı Mahallesi is located 4.35 km northwest of Kozluk district.

The length of the water tunnel, which was built in ancient times and is still in use today, is approximately 25.00 m. The tunnel was built with rubble stones. Right next to the entrance, there is a square-planned water reservoir built in the modern period. Village people meet their water needs through pipes in the newly built water reservoir. The water tunnel has recently been repaired with modern mortar. There is the ablution room of the Cevizlik Mosque at the entrance.

Just south of the Cevizlik Mosque, there is a square-planned pool structure made of neatly cut basalt stones. It is said by the local people that there is an ancient tomb structure in the pool.