Pictured: Inağzı Cave, Zonguldak, Turkey.
A team of explorers venture through a series of incredible caves filled with huge stalagmites and underwater lakes.
The adventurers are carrying out tests in the subterranean world to work out how old the caves are and how they were formed.
The intriguing images were captured in caves across Turkey by amateur photographer Ertuğrul Kulaksizoglu. SEE OUR COPY FOR FULL DETAILS.
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