The imperium always has the settle tile. Sometimes the AI will settle two closely to make this tile visible at times, but it is there from the beginning of the game.
Hmm...there is no visible place to settle in my save game. I'll try to post a link to a save game shortly. I figured it was because the golems started roaming around the map and I haven't found them all.
Here is a link to the save game. I have a pioneer unit in Imperium waiting to settle the area. It is to the north on the map.