Postmark is a tiny little place right behind the Lenin statue in Fremont. The store is mostly taken up by a giant cooler with dozens of kinds of gelato and sorbetto, and the walls are plastered with dozens of postcards and posters. They sell panini sandwiches and such, but the gelato's really the main reason to come here.
The servers will give you a taste of any of the gelatos; try a few, then order a combination that sounds good to you. A (generously sized) small dish comes with two scoops, a medium with three and a large with four, so there's room to experiment. Chocolate-orange, coconut-pineapple, hazelnut-strawberry-jalepeno (yes, strawberry-jalepeno is a flavor -- taste before you order). A lot of sweet icy goodness for a fair price.