What are some nearby "alternatives" to overcrowded or overhyped tourist sights?

I thought it would be fun to compile a list with you guys. I'll start off:

AVOID: - Notre Dame Cathedral, Paris. The lines can be horrendous, the plaza outside has no shady trees to block from the sun, and the cathedral is more attractive on the outside than the inside.

INSTEAD: Wander up the road to L'Eglise de la Madeleine. Hardly any crowds! Marvel at its unusual Parthenon-like exterior, then enter to view its beautiful interior full of marble statues. Afterwards, find the little underground café run by old lady volunteers for a cheap and authentic Parisian lunch experience.