I don't like to be verbose, so I'll get straight to the point.
I want to offer you a game:
You have to select one of the available (green) dungeons from the list.
Go there, find an interesting spot, put this Lovely Cake on the ground (to prove that this is a new screenshot and you're not in offline mode) and smile to the camera.
It's simple, but eventually we will have a full list of places that we can explore.
List of the instances:
Dungeons and scenarios:
A Brewing Storm
A Little Patience
Abyssal Maw: Throne of the Tides
Arena of Annihilation
Assault on Zan'vess
Auchindoun: Auchenai Crypts
Auchindoun: Mana-Tombs
Auchindoun: Sethekk Halls
Auchindoun: Shadow Labyrinth
Azjol-Nerub: Ahn'kahet: The Old Kingdom
Azjol-Nerub: Azjol-Nerub
Baradin Hold
Battle on the High Seas
Black Temple
Blackfathom Deeps
Blackrock Caverns
Blackrock Depths
Blackrock Spire
Blackwing Descent
Blackwing Lair
Blood in the Snow
Brewmoon Festival
Caverns of Time: Hyjal Summit
Caverns of Time: Old Hillsbrad Foothills
Caverns of Time: The Black Morass
Caverns of Time: The Culling of Stratholme
Celestial Tournament
Coilfang Reservoir: Serpentshrine Cavern
Coilfang Reservoir: The Slave Pens
Coilfang Reservoir: The Steamvault
Coilfang Reservoir: The Underbog
Crusaders' Coliseum: Trial of the Champion
Crusaders' Coliseum: Trial of the Crusader
Crypt of Forgotten Kings
Dagger in the Dark
Dark Heart of Pandaria
Dire Maul
Domination Point
Dragon Soul
Drak'Tharon Keep
End Time
Fall of Shan Bu
Firelands
Gate of the Setting Sun
Gnomeregan
Greenstone Village
Grim Batol
Gruul's Lair
Gundrak
Halls of Origination
Heart of Fear
Hellfire Citadel: Hellfire Ramparts
Hellfire Citadel: Magtheridon's Lair
Hellfire Citadel: The Blood Furnace
Hellfire Citadel: The Shattered Halls
Hour of Twilight
Icecrown Citadel
Icecrown Citadel: Halls of Reflection
Icecrown Citadel: Pit of Saron
Icecrown Citadel: The Forge of Souls
Karazhan
Lion's Landing
Lost City of the Tol'vir
Magisters' Terrace
Maraudon
Mogu'shan Palace
Mogu'shan Vaults
Molten Core
Naxxramas
Onyxia's Lair
Peak of Serenity
Proving Grounds
Pursuing the Black Harvest
Ragefire Chasm
Razorfen Downs
Razorfen Kraul
Ruins of Ahn'Qiraj
Scarlet Halls
Scarlet Monastery
Scholomance
Shado-Pan Monastery
Shadowfang Keep
Siege of Niuzao Temple
Siege of Orgrimmar
Stormsea Landing
Stormstout Brewery
Stratholme
Sunken Temple
Sunwell Plateau
Tempest Keep: The Arcatraz
Tempest Keep: The Botanica
Tempest Keep: The Eye
Tempest Keep: The Mechanar
Temple of Ahn'Qiraj
Temple of the Jade Serpent
Terrace of Endless Spring
The Bastion of Twilight
The Deadmines
The Nexus: The Eye of Eternity
The Nexus: The Nexus
The Nexus: The Oculus
The Secret Ingredient
The Secrets of Ragefire
The Stockade
The Stonecore
The Violet Hold
The Vortex Pinnacle
Theramore's Fall
Throne of the Four Winds
Throne of Thunder
To the Skies
Troves of the Thunder King
Uldaman
Ulduar
Ulduar: Halls of Lightning
Ulduar: Halls of Stone
Unga Ingoo
Utgarde Keep: Utgarde Keep
Utgarde Keep: Utgarde Pinnacle
Vault of Archavon
Wailing Caverns
Well of Eternity
Wyrmrest Temple: The Obsidian Sanctum
Wyrmrest Temple: The Ruby Sanctum
Zul'Aman
Zul'Farrak
Zul'Gurub
Arenas and battlegrounds:
Alterac Valley
Arathi Basin
Blade's Edge Arena
Dalaran Arena
Deepwind Gorge
Eye of the Storm
Isle of Conquest
Nagrand Arena
Ruins of Lordaeron
Silvershard Mines
Strand of the Ancients
Temple of Kotmogu
The Battle for Gilneas
The Ring of Valor
The Tiger's Peak
Tol'viron Arena
Twin Peaks
Warsong Gulch
Other:
Acherus: The Ebon Hold
Darkmoon Faire
Deepholm
Deeprun Tram
Gilneas
Kezan
Molten Front
The Lost Isles