As per usual with Agents of S.H.I.E.L.D., last night's episode answered one question as it opened up a water cooler's worth of new ones.
Coulson and his new pal, Mr. Thompson, finally unvieled what Coulson's been doodling throughout the second season. All those circles shapes and lines? They're not a map, as most people speculated. They are a set of blueprints for an unnamed city. Now that Coulson, and his agents, understand what they're dealing with, it's likely that the season will soon shift gears towards locating and exploring this secret Metropolis.
But what city could these blueprints unfold? The Marvel Universe hosts plenty of exotic locale that S.H.I.E.L.D. explore and establish for future films. While there are dozens to choose from, here are the most likely cities to get a visit from Coulson and his crew.
The home of Marvel's Inhumans, Attilan has secretly resided in the heart of the Arctic for hundreds of centuries. Marvel's Inhumans are a race of genetically superior beings. Bestowed advanced intellect and abilities from an alien race at the dawn of mankind, the Inhumans isolated themselves from the rest of Earth's homo sapiens and existed independently. With an Inhumans movie slated for 2018, Marvel has made it no secret that they will brand the Inhumans as their own Mutants (Fox currently holds all film rights to all X-Men intellectual properties). While Inhumans is still years away, Marvel may be eager to build a fanbase for the still-relatively obscure property as soon as possible.
Wakanda is a secluded African nation that, technologically, is light years beyond the rest of civilization. But more importantly, the city is led by none other than Black Panther, the latest Avenger to get his own solo film from Marvel Studios. Now that the world can officially anticipate a Black Panther film, Marvel will want to start planting seeds for T'Challa's world. Iron Man 2 made it clear that S.H.I.E.L.D. knows of Wakanda's existence, as it appeared on a map inside Agent Coulson's S.H.I.E.L.D. base.
Like most fictional universes, Marvel has their own interpretation of the lost underwater kingdom. Marvel's Atlantis and the surface world have had a rocky relationship at best. (The oceanic civilization did set a tidal wave on Manhattan, after all.) Atlantis is ruled by King Namor, The Sub-Mariner. Though once an enemy to Marvel's heroes, he eventually joined Captain America on the frontlines of World War II and became a supporting ally to the Fantastic Four. As an entire civilization, Atlantis holds a ton of potential characters and concepts. Marvel hasn't alluded to any plans for Atlantis yet, but Agents of S.H.I.E.L.D. seems like the perfect place to test them out. The Avengers are going to need all the help they can get for the Infinity War, after all.
It's definitely the least exciting possibility, but Thor's homeworld could be making another appearance on Agents of SHIELD. Thor's Asgardian companions made a guest-appearance during Season One, so a relationship between the worlds is already established. With the door between Midgard and Asgard kinda open, it wouldn't be too much of a stretch to think that Coulson might have a mission in the realm of the Gods. His motives could entail anything, but at the very least, we're sure he's just dying to reconnect with Loki.