My personal favorite is seeing - and touching* - the Spaceship Shuttle Enterprise during the 1984 World Fair in New Orleans. It was (and still is) overwhelmingly beautiful and impressive by its structural soundness. I recalled how delighted I was when it was christened "Enterprise" as I'm a Trekkie. One can imagine how I followed its missions - as well as all other space missions.
It's ironic that after all those successful missions the Enterprise finally got a ding on its wingtip during transport past a bridge support on its way to a temporary port before its installation at the Intrepid Sea, Air & Space Museum in New York City.
(*During those golden years one was still allowed to touch historic icons, including the Liberty Bell when it was originally stationed in Independence Hall.)