Land reserved

[Neofita]

I have a clean map.
I worked on a sea shore.I want to build port and seawall.
I can not, however, in some places to put anything,because when I want something to put,the game tells me---"Land reserved"
and that in places where it was building a nothing.
what's going on.   

[Andreas]

Try the dezoning tool - if it displays some costs, there were invisible zones (or whatever) that get cleaned, and you might be able to use the tiles for building again.