Seems there are multiple sites that sell the 'Secret Itineraries' tour for Doge's Palace. Is it all the same outfit, or are they competitors? If they are competitors, which one is considered best [regardless of price]?
A quick search shows a 'Secret' tour can be booked at www.tickitaly.com, www.veniceconnected.com, & ww.hiddenvenicetours.com. Probably more.
Cheers, & thanks in advance for any info...