Question dont know when its safe to leave the settlement during city building

[starscreamM14]

hi, i dont know when its safe to leave the settlement during building.
in the tutorial up on youtube kingath exits that flying cinematic mode after he gets a message "new city construction"
but the problem is whilst building some cities this message wont appear.
i just wait and wait and wait and construction seemingly stops, because i cant see anything new being added, but nothgin else happens.