When you see such a warning, PAZI MINE, should respect it very strictly, there are still a lot of mines and bombs left in the area of the town. Vukovar is in a way a Croatin Stalingrad, there was a severe battle here in 1991. The seage of the town lasted several months and all this area was "showered" with the bombs, few thousands of bombs were launched at the town every single day.
Please do not enter the destroyed buildings. Some parts of them have such a big structural damage that it is very dangerous to go inside. Plus, inside might be unexploded mines.
The surrounding areas of Vukovar are potential mine fields. If you see sign saying MINE respect it! Even if it is only a suspictious area do not be the one who will test it - this is not the video game and you have no additional life.
The best is to stay on paved paths and avoid any other surfaces.
Since the civil war in former Yugoslavia started, Vukovar was a city among the first ones which was attacked. Serbian soldiers attacked Vukovar, and still today 2010 you can see memories from the stupid and crazy war. I saw so many damaged buildngs and ome still have holes after the ammuniation from the Serbian soldiers. But let us hope that the inhabitants in Vukvar will build up this beautiful city. I know that EU give them a lot of money to do that, so I hope they use it well.