We are going on a 16 day trip in late september early october to the four above mentioned cities. We plan on flying into Paris, traveling by train from there to Brussels, then to Munich and finally to Rome. We then plan on flying Rome to Paris to catch our return flight out of Paris. We will have 3-4 days in each city depending on how long the train ride takes. I know this is a very general outline, so I guess we are just looking for general observations/suggestions about our plans and if we will run into any major issues. Also, in Rome, our top three priorities are ruins, food, and cafes in that order. With those three things in mind, what are a couple of good day trips to look into? Thanks in advance.

Forgot to mention this in the original post.

We will be in Munich for Oktoberfest, but if by some miracle we tire of drinking good beer, what are some good things to see in or around Munich? We are both history nerds so anything old would interst us. Thanks again.

Plane tickets already purchased? If not, look in to an open jaw - in to Paris and then out of Rome. Saves returning to Paris from Rome.

I live in Brussels so can share some tips on what to do here. Brussels is a lot smaller than the other cities on your trip, so you might only want to spend 2-3 days here, or plan for some day trips to nearby cities like Brugge or Antwerp (easy to get to by train). The tourist area in Brussels is around the Grand Place - a must see, but I would avoid eating/staying in this area too much. The Sablon area is very nice - loads of little shops and chocolate stores. Here is a little walking tour idea for this area - http://bestofbrusselsblog.com/2011/1...-with-friends/
Other favorite areas for shopping are Ave Louise or Rue Dansaert.
There are some unique museums in Brussels like the Musical Instrument Museum or the Coudenberg underground palace ruins. See here - http://bestofbrusselsblog.com/2011/1...at-the-museum/
And of course there is the food! There are more restaurants in Brussels per capita than any other European city. Belgians love their food and there are tons of great places to eat. You can see my top picks here - http://bestofbrusselsblog.com/category/food-drink/
Hope you have a great visit!

You should consider a day trip to Ostia Antica from Rome. I often think people would understand Rome and its Forum better if they saw Ostia Antica before they saw the Forum. The Baths of Caracalla are also a thrill for anyone interested in Rome's antiquity.

I don't think you should make cafes in Rome a big priority. There are a few good cups of coffee to be had in Rome, but drinking coffee is done on the run. You can track down some "historic" caffes, but nothing like what you would find in northern Italy or in Naples. (Belgium has better caffes than Rome, and it certainly has delicious food, but I prefer Belgian towns like Antwerp or Ghent to Brussels, although the Grand Place is very much worth looking at.)