2 hours including security check
If I remember correctly it was about 2 hours
It took at least 90 minutes and you could stay and look around on your own after the tour was done. We also went outside to the stands and bought some souvenirs and to their soccer team store for some soccer clothing.
If memory serves me correctly,the tour was at least an hour and a half. That is just the tour itself, doesn't mean you have to leave right after. You can stay as long as you like right after the tour and I recommend that you do. After, I highly recommend you go to the restaurant called " Picca-Dilly Alta Taverna". They have some amazing "Jamon" that you must try. They are two minutes away on "Marina 237". It's a side street just minutes from the cathedral. You will not regret the tour or the Taverna.
I would agree; 90 minutes with as much time as we wanted to stay inside afterward.
We had a 90 minute tour. Time and money well worth it. We then stayed a little longer to take in more of the magnificent building.