Niccolo's place is literally 3 minutes walking distance from the train station and about a 6 minute walk from the church that houses Da Vinci's The Last Supper (make reservations if you want to see this btw, they sell out weeks in advance.)
Niccolo was really responsive and a chill host, he was great about check-in, was flexible with our changing arrival time and the apartment is clean with all the amenities you need, including a coffee machine! Great AC if you need it and plenty of hot water and towels and the bed is comfy.
The central location made it a perfect hub and we were able to catch a high-speed train to the airport just a few blocks away (at the same station as the Cadorna stop on the Metro.) Everything else, including the Duomo and the Navigli district, is about a 20-30 minute walk. Great restaurants and shopping in the vicinity!
Highly suggest this place.