For the most part, when I go on vacations, I generally don't go for exploring reasons. Doubly so when I'm on vacation with my family. A recent trip I took to Florida & the Keys is no exception... this was not an exploring trip.
However, when we visited Everglades National Park, I saw a sign regarding tours at the Nike Missile Site HM-69 within the park. So we checked it out, and I'm glad we did. While it may bother some of the purists in this hobby that it was on a public tour, as opposed to sneaking into the grounds, I've added it to the site. Simply, because it's a Cold War relic (which I can't get enough of), and because it's nice to see the National Park Service making this part of history accessible to people.
It was laid out similar to a Doors Open event, so it counts as one as far as I'm concerned.