We stayed one night at 6 Porte in Mantova, and we enjoyed it. The host is amazing, helped us to schedule our visit to the historical centre, a short ride from the guest house, there is free parking and free shuttle.
The room was clean, the bathroom huge. The system to cool and heat the room is somehow inefficient.
No fridge in the room, but available for purchase at decent prices were wine, beer, ice cream.
The breakfast was nice, plenty of sweet pies and pastries and fruits, nice coffee.
The site is very close to the highway.
We recommend 6 Porte Guesthouse, for sure.