Someone should remind the Pope that walls saved Christendom from Islam. Constantinople's walls held it back for 500 years but those walls failed and we know the sad outcome. Luckily, the Walls of Vienna held off Islam, twice or Islam would have advance deep into Germany and maybe beyond. A section of the old bastions (Molkerbastei) preserved to retain an old house and a relief celebrating the 1683 fights which took place on that site (The relief shows Christian soldiers behind a wall killing invading Turkish Muslims).