The museum with the LH742 is in Speyer, the one with the Concorde and Tu-144 is in Sinsheim. I've been to both and the amount of exhibits is quite impressive, whereas the conservation is sometimes lacking... sometimes bad enough to make an aviation nut's heart bleed. Nevertheless, they are of course a must if you're anwhere near them and have the time. I'd call a visit to either of them a day trip, although you can of course happen to have some time left at the end. In Speyer, there's also "SeaLife
" and the magnificent dome and historic centre, which are all highly recommendable.
As for Heidelberg, well, I live here - we have some amazingly ugly parts and then some rather beautiful parts which I seldom have the opportunity to appreciate; they are off my daily track. First of all, there are about 27,000 students at the university while the entire city has some 140,000 inhabitants. So it's quite a young population. The historic part ("Altstadt", in German) is full of good-looking buildings, but I've grown up in a picturesque town packed with those cute little timbered houses and been in Heidelberg for too long to notice anything sensational in the city. In a way, I'm used to seeing houses that are more than 400 years old.
That said, I do like it here a lot. The castle sits nicely above the Altstadt, you have a centre that's full of life at almost any hour you might find yourself there. Heidelberg is right where the Neckar river enters the Rhine plains from the East, and one morning in October, the combined rays of the rising sun and the usual fog billowing from the valley early in the day made for one of those moments that make you love your city.
I'd offer to buy you a glass of wine when you're here, but have no idea where I'll be in April - so I won't promise anything I don't know I can keep.
Edit: a German "Dom" is, of course, an English "cathedral"... not a "dome".
[Edited 2006-01-17 00:52:37]
Don't cry because it's over, smile because it happened.