So many of these things already listed!
Rome is my favourite place in the world, despite having been a long haul stewardess for 20 years. I love the Trevi and the Roman forum. I also love the Cinque Terre in Italy.
Gorge and Canyon du Verdon in France - I loved it more than the Grand Canyon.
Pyramids near Mexico City (forgot the names), impressed me more than the Cairo ones, perhaps because you can climb them? I would love to see more Egyptian ruins though.
Rio- Corcovado and Sugarloaf both impressed me, in fact all of Rio is amazing!
Eifle tower. I spent a year living with it outside my bedroom window and never got bored of it lit up.
Lots of uk places are pretty special too. I never get tired of the view flying over London on the approach to Heathrow.
Oh and the Great Wall in China (and the slide down it!), the forbidden city and the Ming tombs were pretty special, but otherwise I don't like China as a modern country, but its historic remains are wonderful.