SLC.
When I got my first "real" job in the early 2000's, I took my paychecks which I incorrectly thought were impressive and frequently bought plane tickets. I can comfortably say I've added most of the lower 48's "major" airports (without accepting any formal definition of "major"), and nearly all of the hub airports, with the bizarre and glaring exception of SLC. Hub for a srsly major airline, that is, and I've never connected there.
Also I've not landed at BWI. Not a hub, I know, but obviously Balto. is a major city and I love cities. I'm given to believe that it has a B&O Railroad Museum, a Baltimore Streetcar Museum, a National Marimatime Museum, a Shot Tower, an original Washington Monument, an H. L. Mencken house, and a Museum of Public Works; so it sounds like a city I could really enjoy spending three or four days in. Instead, I've never even landed at their airport.
Nor at SLC.
And I'm surprised by that.
When you look at your I-Landed-There List, do you see any surprising lacunae yes LACUNAE???