Are you required to leave your car unlocked and the keys inside when using the parking garages at Venice?

We parked in a lot at Mestre, left some luggage (not any valuable stuff) in it, took the keys, then the bus into Venice.

We returned 7 days later, picked up the car and paid €50.

I found my answer via google.....you are NOT required to leave your keys or your car unlocked at Troncehetto but you are required to do so at San Marco....

Have no idea where you could leave a car at San Marco - it's in the middle of Venice and nowhere near a road.

If you mean Piazzele Roma - the end of the causeway into Venice with the giant parking garage - no you keep your key - and park your car backed in - so the trunk is next to the wall. And you leave NOTHING - inside the car or trunk.

I should have said Garage San Marco
at Piazzele Roma.... according to the Venice Info site on Google you must leave your keys and your car unlocked at THIS garage. No big deal...I have decided to park at Mestre and take the train in.