On Silversea Cruises, even the upper crust flips for the bottom crust — of pizza, that is. The Italian cruise line uses only house- made dough, hand-tossed and stretched to order, resulting in billowy, golden- crusted pies. For popular pizza crudaiola, the dough is baked with secret- recipe tomato sauce and buffalo mozzarella, strewn with arugula and chopped tomatoes, and drizzled with extra-virgin olive oil. Pizza quattro stagioni has countless devotees; each pie quarter is topped differently, with primo ingredients such as fresh artichoke hearts and hand- sliced prosciutto — the same served in the ships’ fine- dining Italian restaurants. Or play diva and order a custom pie. Flaky crab pizza, anyone?