When was the last time there was a landlocked body of water bigger than the Caspian?
The Tethys, which was previously an ocean, became landlocked by the Indian subcontinent to form a massive body of water before the Indian plate collided with the Euarasian to form the Himalayas (about 250-400 Ma).

I don't see any visuals on the Tethys as a sea (as opposed to when it was an ocean) widely disseminated on the web. Here's an approximate diagram from my memory of a textbook: