I went to Italy with 4 lenses; the Tokina 11-16, the Nikon midrange I will describe, a nikon 50mm 1.8 and a nikon 135mm 2.8. I would say that my breakdown of use was 40% / 40% / 10% / 10%. Although we went to a lot of churches, visiting churches was a big reason for going.
The Tokina is the best UWA you can buy for a crop sensor camera, for photo or video. There's literally no better option.
Buy one of those up if you can.... They are great for the interior of buildings and whatnot, especially dark churches and cathedrals.
Since buying that will leave you strapped for cash, the other lens I would suggest is this:
Nikon 28-80 f3.3-5.6. You can pick it up for less than 100 bucks, check craigslist and ebay.
Before you laugh:
That's a shitty old kit lens from the days of the d70 / d50. However the only thing that's shitty about it is the aperture range (doesn't do low light) and the build quality (which is fine as long as you don't drop it)
It has very little distortion, almost no abberation, no haloing or flaring, and it's REALLY sharp. Just a testament to how well nikon makes lenses (The 18-55 you had is actually a really sharp and contrasty lens to, but it has distortion issues.) added bonus for travel - it's VERY light. it weighs about as much as the 50mm 1.8
There's a shot of Giray Dadali in SBC skier with that lens. you can also check my slowly updated (the photos in it now are just the first three days) Italy photoset on flickr:
As for a bag:
I don't know how it is in Germany, but if you're carrying a backpack into churches and landmarks in Italy, they will ask you to check them. I carried this man-purse looking Domke bag (which is nohomo in EU, all the dudes have them)
Since everyone has them, they allowed me to take it (With all my gear) into places I might not have been able to take a backpack (like St. Peter's Basilica).
Also, since they are on your side, it's harder for pickpockets to get into them without you noticing (almost impossible) and people who might try to steal your shit if they noticed a camera bag won't be as keen on it. I had people try to get into my bag a couple times while I was traveling.