Probably my best memories are not due solely to location but also due to who I was with.
Zion National Park is my favorite place on the planet. I first went there on a driving tour of Arches, Canyonlands, Zion, Bryce, and the Grand Canyon, with my daughter while she was still in high school. I went back with my wife after I had recovered from a heart attack. Stayed in the Desert Pearl Inn both times, hiked Angel's Landing among others, wife had the "best meal I've ever had" at a now defunct 4 or 5 star ? restaurant. Went in May before the crowds of summer - it was great. I was halfway looking at real estate in Springdale, UT.
Had several great visits to Lake City, CO. Once with just my son, once with just my daughter, once with everybody, once by myself (wife is not a fan of the dropoffs). Rented jeeps and ATVs for riding, bought a Jeep, and had a great time driving various mountain roads - Engineer, Cinnamon, Yankee Boy, Imogene. Rode the Durango to Silverton steam train. Stayed at Pleasant View Resort in Lake City, which is not deluxe but I thought it was neat. Had a disconcerting bear encounter in the city limits of Lake City. Great scenery and memories. Great ice cream in Lake City although it turned out to just be Edy's - funny how that is.
First trip to Europe the family went to Germany and France. It was memorable for how bad it was. Kind of a WWII tour. Went to Paris, Remagen, Nuremberg, Normandy, Eagle's Nest, etc. We did everything wrong. Everything. One place we stayed had a GLASS door in the bathroom that opened into the hall - I kid you not. My wife, who had made all of the reservations, was crying. Now it is funny and is part of the family lore. Cab ride in Paris was life changing for its fearsomeness.

Best trips have been to London. There is a lot to be said for going to English speaking countries although we can get by pretty well with German but not at all with French. There is also a lot to be said for (well run) train travel. Had maybe the best steak I ever had in London. Really enjoyed Bletchley Park (codebreakers) of course and Cambridge.