I saw it a month ago. Surprised I didn't notice it before considering Sarum was the first map I played on.
It's one of those boss arenas on maps. I believe there are two on Sarum. Their entrances are somewhere in between two teams. As of now, the arenas look cool but are essentially useless. Whoever that placed the tp there probably just want to create misery because it's god damn hard to get out of there.
LOL i saw this 1st time i played it , i remember every map i played i go scout and discover it . You can find alot of cool places like andorra there's many hidden places that u can find