The actress and her husband Taylor Hackford bought the 16th century fortified farmhouse in 2007 - and they're still paying for renovations before they can move in.
Mirren says, "It is at the bottom of the heel of the boot of Italy and it's not finished. It's like turning on the taps full and money just pours out into it. It will be beautiful but it's not finished.
"It's not really a castle; it's actually a farmhouse but it's got a little bit where you can pour boiling oil out of it because, in history, Puglia was being invaded all the time with endless invasions, so even the farmhouses are fortified."