How to access this optional area?

I've played through the games many times but still can't figure out this area. It has a cacodemon here and that's it. But I see a gore nest up top on another platform that is inaccessible. How to get there?

https://preview.redd.it/itr04v3s907f1.png?width=1920&format=png&auto=webp&s=f72defb834507416b69fd159b27d0afa00af8f20

https://preview.redd.it/s782ps3s907f1.png?width=1920&format=png&auto=webp&s=92c492c5dea0466cb1ae6768a433a48d2653b1a1