Air France and KLM’s Flying Blue program releases a list of promotional destinations every couple of months that are redeemable for half the usual number of miles. They just announced the latest list of destinations that are bookable from April 29 (earlier for Flying Blue elites) for travel between May 1 and June 30, 2013, that you can access here.
Thing to note is that you can book these also as one-way. These are not only for originating from Europe as all the destinations are valid for both directions. Awards allow the origin/destination in Europe to be in zones 1, 2, and 3, basically meaning that these awards are valid from/to anywhere in Europe.