Prut Toltres (Toltrele Prutului), also known as Prut Rocks (Stâncile Prutului), are a chain of limestone reef formations, over a distance of about 200 km along the middle of Prut river in Moldova. It starts from Criva, near the northern border area of the country and continues to Cobani, 200 km further south. They are natural monuments and protected by law. These chains are made of limestone reefs of corals, mollusks, clams, algae and other marine organisms that filled the Tortonian and Sarmatic tropical seas 10 - 20 millions years ago.