I'm starting to think about this, and there are always the things that any out of town visitor would think of and do on their own. We've had out of town visitors come in and ask if we might take them to Fisherman's Wharf, Golden Gate Park, Muir Woods, the Golden Gate Bridge, SF Chinatown, etc. Often they'd go there on their own.
But then there are the places where I might bring a guest, where they'll say "Thank - I would have never thought of going there." We have a nearby regional park that's we've occasionally taken guests to see. And even though some visitors might think of Vista Point to see the Golden Gate Bridge, they might not think of taking the view from Conzelman Road, even though it's been used for many movies.
But I don't know about 50 miles. If I were serious about taking visitors some place they'd never forget, I'd take them to Lake Tahoe or Yosemite. That's more than 50 miles, but what I would consider the best that I could offer.