What sites and/or day trips from Koblenz would you suggest for a 19-year-old? He speaks German well. He has three days to entertain himself in the Koblenz area.

Cologne for the humungous cathedral and riverfront

The Rhine River cruises on KD boats from Rudesheim/Bingen to Koblenz (take train down ride with current back to Kobelnz)

The Mosel Valley - can boat to Cochem or train there - and one of the most beautiful parts of the Mosel Valley, which most consider far more scenic than the Rhine Gorge

Burg Eltz, between Koblenz and Cochem at Moselkern - one of Germany's most famous castles.

In Koblenz don't miss the massive fortress Ehrenbreit??? (sp?) across the Rhine from town and perhced high on a cliff overlooking the Rhine - a chair lift goes up - there is a Youth Hostel in the castle. and the Deutsches Eck (sp?) monument at the confluence of the Mosel and Rhine right in Koblenz - very famous in Germany it once had an equestrian statue of Kaiser Wilhelm perched on it but at the end of WWII an American tank on the opposite bank of the Mosel thought it would be fun to smash the statue to smitereens so firebombed it to pieces. Now a statue in honor of Germany Unity (not the recent one but the one from the 1800s) tops the famous statue.