https://www.pcgamer.com/pubg-is-working-on-an-underground-cave-system-for-its-new-savage-map/

PlayerUnknown's Battlegrounds developer PUBG Corp plans to grow its in-testing 4x4 Savage Map over the coming months. Based on South East Asia, the new arena draws from real-world Thailand—and the battle royale 'em up's latest Steam Community Update post contains photos of Phraya Nakhon Cave following a recent studio visit to Thailand. In-game, part of this landmark will be reworked into an underground cave system. 

"How’d you like to drop from the plane and try to hit a hole like this? That’d be badass right? That’s exactly what we were thinking, which is why we’re working on an underground cave system with plenty methods of escape," reads the post. "We were inspired by a cave system the team found outside of Bangkok."