Cibalo said:
Thanks I will take a look.
Train from London to Frankfurt is about 7hr and $350 for all 4 of us.
A flight is about 3 hr and over $800 once you add in all the fees.
Bigger question, why Frankfurt?
The trans country trains can be a little more tricky. Some are express, some have lots of stops. DB (German) trains has a good website to search
Unfortunately, rail booking is disaggregated from my experience vs air travel booking.
Like others have said, focus on what cities you want to do, then look at the travel route, then back into activities.
Some could be all day travel, some just a few hours.
Leave plenty of time at European airports. It's nothing like being able to show up 30 minutes before boarding and blast through TSA precheck in the states.
Also, don't count out bus travel if you're trying to save some money.