[liamph]

It is interesting to also consider dry land which is below sea level. "For an average height person standing on a beach, their horizon is around 4.5km away." For an average height person standing at sea level, near a large depression such as the Dead Sea, for example, you may be able to see land at a much greater distance.

I doubt if this factor would impact your findings for the longest sight lines on Earth, but perhaps for some local findings.

Also, applying the same concept to other planets has some surprising results. The tallest mountain in the solar system, Olympus Mons, has very gentle slopes. So gentle that from the peak all you can see is Olympus Mons itself.

[tombh]

Yes! These are very much the kinds of questions I'm interested in. The search for the single longest line of sight on Earth is just an excuse to play around in this space.