*Central Europe - sorry for the typo.

For Berlin you might want to try to find this book: Peter Fritzsche and Karen Hewitt, Berlinwalks, 1994 which divides Berlin into 5 different walks in different neighborhoods. Try www.abebooks.com to find a used copy.

http://www.flickr.com/photos/mksfca/sets/72157623174831107/

I personally like Luxembourg - you could do it as a day trip from Brussels, which you can do in 1 - 2 days. Luxembourg is worth a day. It's a gentle little city. Visit the casemates (fortifications built into the cliffs) and the old city, which is down in a valley.

In Brussels look for the Art Nouveau walks from the tourist information centre, and also visit the Horta Museum, which is a must. You can do the Grand' Place, Galeries St Hubert, Grand and Petit Sablon in a day, or a half-day if you don't linger over lunch. However, food is very important in Belgium so do try to factor in a good meal in a nice restaurant (if you're on a budget, try to plan for this event). You won't be disappointed. For a snack, have a waffle at Dandoy.

In Frankfurt spend a day in the city, a day in the surrounds (Mainz and Rhine gorge).

Unless you particularly like museums the best part of Cologne is the cathedral (the cityscape is not that attractive, but the cathedral, considering it's medieval, is an imposing miracle). You can see the cathedral easily from the railway station - stow your bag in a locker and take 1 - 2 hours to enter the cathedral and go up to the top for mind-blowing views. The day you travel from Frankfurt to Brussels would be a good day to do this.

Save Heidelberg for another time. You will come back. It's nice but not critical to see if you've got other things doing.

Lavandula

Thanks for your advice Lavandula, it definately makes sense to add time in Brussels and visit Cologne on the way from Frankfurt.

Your itinerary looks quite good. I am also a photographer and like 'picturesque' places. I have galleries of most of the places on your list. Most of the places you mention are very photogenic. http://www.pbase.com/annforcier

From Luxembourg, you could do an easy day trip to Trier, and also to either Nancy or Metz, as well as the WWII site of Diekirch - it's a beautiful drive from Luxembourg City through the woods. On the way to Brussels, if you're a WWII buff, stop off in Bastogne and vicinity.