Easton's Bible Dictionary: M. G. Easton, M.A., D.D.
Fountain of the sun a spring which formed one of the landmarks on the boundary between Judah and Benjamin (Josh. 15:7, 18:17). It was between the "ascent of Adummim" and the spring of En-rogel, and hence was on the east of Jerusalem and of the Mount of Olives. It is the modern 'Ain-Haud i.e., the "well of the apostles" about a mile east of Bethany, the only spring on the road to Jericho. The sun shines on it the whole day long.