If you suspect that a building or part of it is being or is illegally constructed, if the site is not properly fenced or the physical planning provisions have been breached, as well as any other irregularities, these are the steps you may take for the purpose of solving the problem:

1. photograph the event if possible;
2. Write a brief statement about the event and describe as precisely as possible how to arrive to the location (if there is a correct address, some visible object, distinctive sign and the like.).
3. Send a statement together with the photo to the municipal services monitoring officer in your city, town or municipality, to the Building Inspection (gradjevinska.inspekcija@mgipu.hr), in writing to the address of the Ministry of Construction and Physical Planning, Ulica Republike Austrije 20, Zagreb or to the nearest branch unit of the inspection in the county.

WHOM TO CALL: and/or Green Phone service for your county (072 123 456) - the report may be sent anonymously, too.
NOTE: You can always call the service 112, especially if it is a matter of great urgency, and during the weekends, holidays or at night