Piazza Mario Motta in Orta San Giulio is the heart of the town and one of the most charming places in Lake Orta. In the piazza, you'll find plenty of restaurants and cafés, as well as my favourite gelateria, and I highly recommend a gelato here 'Pan&Vino gelateria'.
In this piazza, you'll also find the ferries to bring you to Isola San Giulio. You can buy return tickets on board, but you'll have to pay cash. Otherwise, you can find the ticket booth in the piazza, where you can pay by card.