So what is the area near the Royal Wyvern fight in the Witcher 3?

[Talos]

This is my second playthrough of the game because I loved it so much, I am doing it on moderate difficulty or whatever it's called. Had never done this contract before but it's the one with the Royal Wyvern after the two smaller wyverns called 'Phantom of the Trade Route' while doing this contract you're supposed to go through a cave to the top where the Wyvern's are roosting but just before the cave's exit where you're supposed to go through, there's another tunnel leading to the right that I decided to explore, upon entering there were a few chests, a dead body, and some kinda shrine lookin thing, then going further the cave opens up to an open cliffside altar area which had me confused because it totally looks like there could be some kind of battle there, I know it's not a part of the main story becuase I've finished that as well, is it maybe a part of a DLC I haven't installed? because it looks way too cool to just be some abandoned part of the game, it's thoroughly bugging me plz help
Here are some screenshots of the area:
https://steamuserimages-a.akamaihd.net/ugc/171542669191696602/4976F10152AEF3E21FE0C39BE12676F74E714AC2/
a.akamaihd.net/ugc/171542669191696443/7A1502428EE73EDEFB6F2A1F6B14924F3C4754F7/
https://steamuserimages-a.akamaihd.net/ugc/171542669191696267/527A4ADE022715556739FBD3B5F709CCE623AF14/
https://steamuserimages-a.akamaihd.net/ugc/171542669191696086/AB3CFDE167755A9486F9C59C40B9CE032B8940AF/
https://steamuserimages-a.akamaihd.net/ugc/171542669191695013/AB75BCAD42C19CBC4A76BD2674B111FB7A60939B/

[Black Blade]

If you like to ask something abut a game, i recommend posting in the games hub, posting in general forums is not likely to give you best results

Each game on Steam has a Community Hub for it, that has its own forums, that is the best place to ask abut things related to that game, i reported the tread to a mod, that will hopefully move it there
Best of luck

[Meatbug]

It's been a while since i played it, but if i remember correctly, that's where the Hearts of Stone DLC ends.

[natshely]

http://steamcommunity.com/app/292030/discussions/

[G-Force Gaming]

Its for the heart of stone ending

[minami]

Was looking everywhere for this. Finally found an answer thanks to this thread. Commenting some more for google algorithms don't mind me.

Phantom of the Trade Route women statues cave path branches off

(those were my google search keywords)