Those sewer grates everywhere

[Alhanelem]

For such a desolate land, Eorzea sure has an extensive sewer network. It's always puzzled me how these grates are in such random locations all over the world. Maybe they were planning something like the meeble burrows they made for XI or something. Any guesses what they would have been used for?

[Dragonheart]

Another of Tanaka's mysterious thing...

[Elexia]

Like I said before, under Bluefog at least there's a cave system that isn't linked to Cutter's Cry we can't exactly enter and explore, it's actually built up somewhat like a canal style (think toraimarai only with ceruleum and dirt)..so it could honestly just be for decoration, or it could have been entrances to dungeons, we'll never know since he never got a chance to finish the game.

[SwordCoheir]

I'm thinking it's a network made by moblins, either as a way to get around or it was Tanaka's intention to introduce a Moblin Maze Mongers type of instance.

[Teakwood]

Goblin secrets.

[Kiote]

Eorzea has been through 6 Astral and Umbral Eras that have seen the rise and fall of many civilizations. Many of the random pieces of civilization you see can likely be attributed to these lost people.

[Zenaku]

Duskwight Elezen live in caves and caverns developed an acute sense of hearing they also resort to robbery and pillaging to survive, earning them the scorn of their woodland relatives. I'm also guessing they use the sewer to find people so they can rob them blind and take there money lol.

[SwordCoheir]

Eorzea has been through 6 Astral and Umbral Eras that have seen the rise and fall of many civilizations. Many of the random pieces of civilization you see can likely be attributed to these lost people.

So Dalamud shelters created by the Ancients as a just in case measure. XD

[Kagato]

Despite common belief, Miqo'te poop too. Has to be disposed of somewhere. Sewers!

[Ralliare]

In the past civilizations put a damn moon in orbit, suffice to say there's probably tunnels under everything.