There was a spiderweb close to my town.  Every so often a spider would pop out of it, and frequently I'd get a popup window saying that I could not destroy a building because it would make my town non-contiguous, even though I was not trying to destroy anything.  It finally occurred to me that maybe the spider was attacking the town even though I had no notice of it, so I moved my sovereign next to the web and kept killing spider after spider as I researched questing level 2 so that I could destroy the web.  Meanwhile I noticed that it was taking forever to build the farm I had queued up in the town.  When I finally did take the web, I looked at the town, and noticed that it now had negative build times for the buildings I had queued up: