Frankfurt, Regensburg, Munich, and Freiburg

I am going to visit 3 different cities in Germany. The city that i will be arriving in is Frankfurt which is a small area and very quit. The second city I will be visiting is a beautiful and historical city located a little east of Frankfurt which is Regensburg. I am also going to visit a more common know city in Germany which is Munich. It is a more bigger city so their is a lot more places to explore there. The last city I'm going to see is Freiburg, a little near the boarder of France. I thought that it would be really expensive if I just took different trains to each city, but luckily i found a really good price on a train pass to all the cities I'm going to visit.( http://www.eurorailways.com/products/trains_passes/single_country/germany.htm )