First, it's not a binary you're-in-the-tourist-zone or you're not kind of thing. There's a spectrum. Second, often the "real" is only 20 feet from the "for the tourists". Something as simple as sitting down in a park and watching people go by can tell you a lot.

I like to talk to the hotel clerks. On my most recent trip (to Venice), the woman who was at the front desk most days actually lived in Venice (unusual) and she showed us a simple route to St Marks from the hotel (that we would never have found, and that was crowd-free till you came out under the clock tower) and recommended two specific churches to visit that many people miss but which are absolutely beatiful. She also suggested walking around some less popular areas, and we enjoyed that a lot. At first it seems that all of Venice is fake, but there is reality there. I was happy to see a bit of it. I believe people who live in a place will be happy to tell you where the real place is.

First, it's not a binary you're-in-the-tourist-zone-or-you're-not kind of thing. There's a spectrum. Second, often the "real" is only 20 feet from the "for the tourists". Something as simple as sitting down in a park and watching people go by can tell you a lot.

I like to talk to the hotel clerks. On my most recent trip (to Venice), the woman who was at the front desk most days actually lived in Venice (unusual) and she showed us a simple route to St. Marks from the hotel (that we would never have found and that was crowd-free till you came out under the clock tower) and recommended two specific churches to visit that many people miss but which are absolutely beautiful. She also suggested walking around some less popular areas, and we enjoyed that a lot. 

At first it seems that all of Venice is fake, but there is reality there. I was happy to see a bit of it. I believe people who live in a place will be happy to tell you where the real place is.