Need high-level adventure

[DonEsteban]

My group has never played anything higher than level 10. Neither have I, really. But I'd like to try it. So what I need is a decent, short scenario that demonstrates some of the intricacies of high-level D&D. I'm thinking level 13 or probably 15. Do you have any ideas? It can be either a published adventure or just some ideas. And not too long, maybe three to five sessions. It should encompass more than just fights. Maybe a little bit of planewalking, saving (or shattering) empires, that sort of stuff...
I just don't know where to start right now and there doesn't seem to be much published stuff that is any good (or I can't find it).

[FrznTear]

Lord of the Iron Fortress has Planar travel and is for 15th level characters. Haven't read it but it seems neat.

additionally there are a bunch of short adventures for all levels lost in time that can be found here
http://web.archive.org/web/20090123093048/http://wizards.com/default.asp?x=dnd/oa/20030530b&page=1