Anyone figured out how to remove improvements?

I've conquered an enemy city and the previous kingdom did a terrible job using the urban squares. I'm probably missing something obvious.

 

Press CTRL when you are with a worker on the tile. The icons on the worker actions should lit up. It's definitely an unnecessary step, IMO.

 

Well, thank you for the tip. With the late game advent of windmills and water mills the need to do some rearranging is considerable.

 

Urban terrain cannot be converted to wilderness. It's Urban forever. However, what's on an Urban tile can be overwritten by a new improvement. ... The Ctrl button required to be pressed, to overwrite an existing improvement, is there to help prevent accidentally putting a Farm on your Pyramids.

 

Can you plant trees?? Harvest them and move them? It would be understandable if that was a longer process like trees growing back in a region where they were chopped.
But Forestry as a tech should allow planting.