TB of my knowledge the border between Turkey, and Greece still has uncleared landmine fields, and Serbian-Croatian border has uncleared spots too, in spite of the treaty. For clarification, I'm not telling they appeared there because of migrants. No, but my point is one can't pretend EU don't want to build border walls because EU is all migrant-loving place. EU's land border with unstable regions is very short (a patch in Bulgaria, a patch in Greece, Spanish Ceuta & Melilla), and already well-fortified. That's why there's no duscussion.