"Stonehenge is definitely worth a trip IMO. Sure, it's a bit far from London, but there are plenty of things to see and do within a decent distance of the historical site to make your trip worthwhile. Just sticking to the prehistoric theme, you also have Avebury and Sillbury Hill in the vicinity."
There simply are no photos that do it justice. It's equally beautiful and scary.
Ahhh, then you want to visit Southeast Alaska. Small towns trapped on islands with history out the wazoo, totem poles, wild animals, dense forests and amazing trails everywhere. Fishing in spring and cheap cruise tickets in fall. Something for everyone from child to child at heart. I live there and I'm still amazed everyday.
For my Part i can definately recommend going to the Grand Canyon (north or South rim).
Versailles is kind of nice but overcrowded. The Garden of the Chateau is the Highlight.
Don't go on the Eiffeltower. Go to the Montparnasse Tower. there you also have a view over the City together with the Eiffeltower. Or just go to Montmartre, there you'll have good view too. Though it is crowded and you cannot see the Eiffeltower very well