Trying to "show" something on the ground to the meat in the back is futile, unless it's something prominent and isolated by itself like the Grand Canyon, that bigass crater in Arizona, Niagara Falls, etc.
Even something as grandiose as Pike's Peak is lost among the other mountains that surround it, so why point it out? Besides, a 14,000 foot mountain looks like a dirt clod from FL370.
We have a great view up front, and I know I've tried to point out something to the other guy, and it's usually like this: "Okay, you see that discolored area on the ground, two o'clock-ish? Come about two finger-widths to the right. Now about halfway between that and the water tanks at four o'clock, can you see a road... you see it? No? You sure? Well f*** it then."
Now if pointing out something to someone with the same view that I have is that difficult, imagine if only half of the people on board can even see the direction you're looking, and their field of vision is only about 60 degrees. Now figure that it's 50/50 that the sun's in their eyes. And usually about half the windows are scratchy or have condensation on the inside.
So by pointing out something on the ground, all you're doing is annoying everyone on board just to entertain the half-dozen people who might be interested, except that they're probably asleep, in the can, or watching the movie.
Probably the only people who really five a rat's a$s about what's on the gound are the guys who have an airplane boner anyway, and they're probably travelling with a GPS, sectional, and a handheld NAVCOM, so they know what they're looking at before you ever pick up the PA.