Landlocked sea that borders russia and iran

Caspian Sea

Explanation:

The largest lake in the world, or often referred to as a landlocked sea, the Caspian Sea, is the body of water on which both Russia and Iran come out and have borders on it. Iran occupies the southern part of the Caspian Sea, while Russia occupies the northern half of its western part and the northwestern part. The other three countries that have their share in this lake are Kazakhstan, Turkmenistan, and Azerbaijan.

The Caspian Sea is actually a lake, as in order to be classified as a sea it has to be connected with the rest of the ocean and sea waters, and it is not, it is landlocked. It has saline water though, which is why it is referred to as a sea. The saline water in it is there because this lake is a remnant of a once very large ocean, Tethys, that was stretching all the way from Spain to Indonesia, and from the central part of the Indian Ocean to Central Asia. With the movement of the Indian plate toward southern Eurasia, and the African toward western Eurasia, this ocean was closed down. The collision of these plates with he Eurasian caused the formation of numerous mountain chains as well, so Tethys was totally destroyed, only leaving behind it remnants like the Caspian Sea deep inland.