Prosecco is a big, big world and the grapes can come from just about anywhere in a very large swath of Veneto and Friuli. When a bottle says Conegliano Valdobbiadene (pronounce it however you want), it only comes from a small hilly region just north of Venice. Well-drained alluvial soils are ideal for the grapes and the hills make it impossible (and cost prohibitive) to make cheap bulk bubbles. If you want to level-up your sparkling game, this is one place to start.