Final answer:
The Caucasus Mountains are located between the Black Sea and the Caspian Sea.
Step-by-step explanation:
The Caucasus Mountains are a significant mountain range located in the region known as Transcaucasia. They serve as a geographical landmark and create a natural border between two major bodies of water. To address the question: The Caucasus Mountains are situated between the Black Sea to the west and the Caspian Sea to the east. These two seas are crucial to the geographical identity of the region, with the Caspian Sea being the world's largest landlocked body of water, and the Black Sea being connected to the Mediterranean through the Bosporus.