The Ouroboros Zone is actually not level locked; using the Ouroboros Portal is though (level 14). You can get to Ouroboros through the Echo Zones at any level. However, the frozen flame crystals still require you be . . . probably level 10? Maybe 15. I can't remember.
Cimerora is level locked to 35, and The Hive and Abyss are level locked to 45. All PvP Zones are level locked as well (15, 25, 30, 45).
I'm personally ready for all those locks to go away, honestly. "Just" put a pop-up dialogue box when attempting to enter those zones, with a 5 second countdown timer so it can't be dismissed straight away, which says something like "You're about to enter a zone which is beyond your current abilities" blah blah blah, "click Yes to proceed."
And while we're at it, please remove the level locks on the Hero-side Accolades and Vanguard Day Job.