Berlin to Frankfurt is also 4 (ICE) to 7 (IC) hours, and has a bunch of trains every day, and in my experience (pre-Covid) was usually pretty full when I took i

Berlin to Frankfurt is also 4 (ICE) to 7 (IC) hours, and has a bunch of trains every day, and in my experience (pre-Covid) was usually pretty full when I took it. Lots of countries have good rail service that people actively choose over cars or planes between major cities. I find it maddening that my own country can't bring itself to really want that.