I can't agree more with the suggestions for all of Croatia and Budapest.
Frankly, after having been to Venice, I'd never, ever go back.
I took a boat across the Adriatic from Venice to Pula, Croatia. Kind of a crappy boat ride (I hate being inside on a boat), but Pula was very, very nice.
Kind of a sleepy town, but with some amazing historical architecture. Pula boasts the worlds most well preserved Roman amphitheater, which is so well preserved it is still used as a venue for concerts and theatre. Warning, extremely large photograph.
From there, I took a 6 hour ferry ride down the Croatian coast from Pula to Split. It was GORGEOUS.
Nothing like being on a slow moving ferry outside on the deck, sun beating down, with Gorgeous coastline and teal blue water all around. I felt like I was on a Mediterranean cruise, except without the Norwalk Virus.
From Split we went to the Island of Hvar and stayed there a couple of nights. It was wonderful. Party town, Croatia. Babes, beaches and Bacardi drinks.
Also, Dubrovnik was wicked too. That's where the film many castle/wall/coastline related scenes in this season of Game of Thrones.