100 meters of the last building should be kept in an urban environment (it is forbidden to fly in a town or city, not even in a park within an urban environment), as well as for high voltage lines, railway infrastructure and main roads, as well as 30 meters from any person not part of the flight.
In Poland there are many Polish and American military bases, a lot of territory is forbidden to fly and it is advisable to check it very well. In AirMap there are also the bases and in fact anything that has any color then must not fly in it.
Only in green (as long as it does not conflict with the other rules) is it permissible to fly.
Warsaw and several other cities have military headquarters (American) and many of the beaches in the north (the Baltic Sea) are close to military ports.