Iran appears to be constructing a mock-up of the U.S.S. Nimtiz. The ship is not operational. Only 2/3s scale. And not militarily capable of much of anything.
As Eric Schmitt of the New York Times reports, The U.S. Navy and:
... American intelligence analysts surmise that the vessel, which Fifth Fleet wags have nicknamed the Target Barge, is something that Iran could tow to sea, anchor and blow up — while filming the whole thing to make a propaganda point, if, say, the talks with the Western powers over Iran’s nuclear program go south.
Fake ships as part of a strategy for building real nukes, then.
Makes perfect sense.