They look similar to the gateways to parties but narrower and of course there's that dev sense of humor in the messages when you find em...so cool I found my first on "The Entrance" and my second on Level 1 East up high....have at it guys. I've no clue where they exist (if they are only in the caverns) but it's great fun trying to find them!!!! Best of luck to everyone. Well done dev team!!!
Okay if it's a help I found my third on Arjun Plunge and one of my friends just found one in Bortola..so they are everywhere! Edited to add: this "quest" just appears like the one for fireflies as a spot on a street and that starts you out on the quest to find the next 10...a message with each one and pts too! Great fun, enjoy! (And you hear a strange sound when you enter the street where your next one is..kinda like a whoooing..like someone was sort of clanging a gong type bell softly but not quite, maybe someone else has a better way to describe the sound but it's definitely there..so turn on the SOUND peeps so you don't miss one) (4th one was in Alakol)