The Lake Maggiore is 60 km north west of Milan, near the Alps and the swiss border. It extends for about 65 km and it's reachable by train too.
Famous for his fabulous villas, the main points of interest are:
Isola Bella (Beautiful Island - part of Borromean Islands, near Stresa) with the marvellous baroque palace, the Italian style gardens and the fishers village. (https://www.isoleborromee.it/en/)
Villa Taranto Bothanical Gardens (https://www.villataranto.it/en/) in Verbania.
The characteristic Orta San Giulio village in the near Lake of Orta.
Santa Caterina del Sasso hermitage overlooking the lake.
(http://www.santacaterinadelsasso.com/en)
The villages of: Arona, Baveno, Cannobio, Luino
you can travel through the lake by ferries (https://www.navigazionelaghi.it/en/search-results/)