Yes, I created one accidentally when I was playing the FA. I put all my residences into storage, thinking I didn't need the coins but forgot about the population. I went negative. Then I put them all back and went positive again. As stated above, you just can't build anything when you're negative.Have you ever seen a city with negative population?
Well i meant a real city
As i see now, you can also take advantage of this. Just didn't expect this was possible.
I know a player who teleported almost all of his residences during Traders of Unur chapter to build a large fleet and had around -100k pop for one or two months.
And he certainly wasn't alone.