An idle spot is a single patch of land not used, or idle, on your City or Outpost.
How can Idle Spots be used?Edit
Idle spots can be used to build Buildings.
To do that, click on an Idle spot, and choose which building to build. After using a Mass Nulifier, the idle spot will appear where the building once was.
OIL (Other Important Links)Edit
Here are a few links related to Idle Spot.