Vaccaros has simply the best authentic Italian pastries in the city. There are several locations, including two in DC, but I always go to the one in Harbor Place. So good, always fresh and friendly! They can be VERY pricey, though! Cakes can cost up to $70! But treat yourself to a slice of tiramasu next time you're downtown, you won't regret it!
PROS:
CONS: Very expensive!