London is an obvious choice - plenty of touristy things to do. Peru would be about Machu Pichu and Cusco. The Inca ruins should keep you busy for about 4 days. Cairo has similar attractions in terms of ruins. And, of course there's always Athens for Greek ruins.

My parents are like you - they like lots of attractions. They said their best trip was a Mediterranean cruise. Every day, they were someplace with lots to see. Barcelona, Cairo, Athens, etc.