Kree City

The Kree City is an underground city build by the extraterrestrial race, the Kree, a thousand years ago on Earth.

City Blueprints
It was theorized by Dr. Goodman, a medic who worked for Project T.A.H.I.T.I., that the genetic memory of the Guest Host, while attempting integration into the human mind, caused the patients of the project to write the symbols. Eventually, Phil Coulson, an unwilling participant of the project and the director of S.H.I.E.L.D., learned that the symbols were the blueprints of a city and became determined that his organization would find it before anyone else did.

Finding the City
Phil Coulson created a plan that would hack into the satellite feeds of the Laura Creek Station in Australia to find the hidden city. Meanwhile, Calvin Zabo, a doctor who wanted to be united with his daughter who he knew was special, told Daniel Whitehall, a HYDRA General who wished to weaponize a Diviner he obtained in World War II, that the Kree artifact was a key to a temple in the Kree City. Whitehall sent Zabo to Australia with other operatives where they ambushed Coulson and his agents. Zabo escaped without learning the location of the city but Coulson learned its location.