If one traveled the circumference around their Techum on Shabbos (about 12.5k Amos = 2π * 2000), do they have any obligation to say Tefilas HaDerech, being that they traveled more than 2.8 miles (approximate measurement of a Parsa)? And this is assuming there are no nearby houses or metropolitan cities.
In other words, is there ever a case where someone may/must say Tefilas HaDerech on Shabbos?