Cologne-Frankfurt via Koblenz or Neuwied
The railway lines along each bank of the Rhine are the best way to appreciate the beauty of the gorge between these cities, which is regarded as the waterway's most impressive stretch. Both are served by stopping trains, so it is easy to break the journey to visit the many castles that line the banks, though some are a stiff climb into the woods. It's best to make both journeys, as many of the hilltop castles are invisible from the riverbank on which they are situated.
Where: DB (08718 808066; www.bahn.co.uk)
How much £38.54How long 1hrs 30mins-3hrs 30mins