Several legends surround the Drachenfels, most famously that of Siegfried – the hero of the Nibelungenlied – killed the dragon Fafnir, who lived in a cave in the hill, then bathed in its blood to become invulnerable. Hence, the hill is named the "Dragon's Rock",Drachenfels. (source: Wikipedia)
Today you can take a cog railway, horse drawn cart or walk up to the ruins of the castle for spectacular views of the Rhine. There is also a restored castle, Drachenburg, halfway up. Tours are in German, but group tours in other languages can be arranged.