If you go to Paris, I would recommend taking a train out to Versailles Palace. It's absolutely wonderful. The tours can get pretty crowded during the summer, but it's worth it. The grounds are also quite something to see.
Giant’s Causeway made from 40,000 interlocking basalt columns from ancient volcanic eruptions. Science and mythology mingle at the Giants Causeway, formed from volcanic activity some 50 to 60 million years ago.