Has anyone been to Conegliano? It's where they make Prosecco and it's just North of Venice. I heard about it on a radio program and it sounds quite charming.
Haven't been there specifically, but in the general area and the scenery is quite lovely. Try googling "prosecco road" and you'll get a lot of hits about the area.
I've been there a few times. Prosecco is definitely a big deal. There are some nice antique markets in the area. I saw a concert in the industrial area.
Also, a castle: http://www.hotelcastelbrando.com/hotel-treviso-photogallery-en-98.html
Though I haven't been to the castle just yet. Working on it!