Yes, and more here: http://www.ww2f.com/weapons-wwii/12270-german-experimental-weapons-ww2.html Mimoyecques Fortress - V3 base
That's correct - the infamous Iraqi 'supergun' designed IIRC by Gerald Bull ( no relation ! ) who was assassinated by Israeli agents. The V-3 was yet another ingenious idea on which the Germans expended large amounts of time and resources which could have been better utilized elsewhere.....