Scripts

You need to jump into the gates of the enemy city, or into the city itself, if it's your city, even from the gate point.

Then, create an array with the "gate points" at the beginning of the game.

gate_points = {}
function GetGatePoints()
	for i, town in GetObjectNamesByType('TOWN') do
		for j, hero in GetObjectNamesByType('HERO') do
			if IsHeroInTown(hero, town, 1, 0) then
				local x, y, z = GetObjectPosition(hero)
				gate_points[town]={x, y, z}
			end;
		end;
	end;
end;

Added 6 minutes later

No way. And the city should never be empty BEFORE the script runs (that's why it doesn't work).

You can remove the hero from that city using the same function.