I will be making a birthday cake in about a month that needs to be transportable. By this I mean, can it survive a 6-8 hour subway/train trip and not need refrigeration? I've been looking at cake cookbooks, and my main concern is how do I determine which cakes definitely need refrigeration, other than common-sense ones like whipped cream frosting, etc. It doesn't need to be a "traditional" layer cake; my main goal is that it be very tasty and survive the trip. One recipe I am considering trying is a Nutella cake, where Nutella can be used as frosting. Also, a ginger cake from Chowhound (although a frosting would be nice). Any other ideas? Thanks in advance, all you cake experts! I will be test-baking over the next few weeks before making the "real thing".