Yoel Elitzur and Doron Nir-Zevi, “A Rock-hewn Altar Near Shiloh,” Palestine Exploration Quarterly, January-June 2003; and Elitzur and Nir-Zevi, “Mizbeah hazuv ba-Selah mi-Maarav le-Shiloh,” Judea and Samaria Research Studies 12 (2003), pp. 35–48 (in Hebrew).
On the right-hand part of the southeast side, however, is a rounded projection and beside it a depression in the eastern corner. This somewhat mars the square shape of the altar.
A four-horned altar was also found dismantled at Beer-Sheva. See “Horned Altar for Animal Sacrifice Unearthed at Beer-Sheva,” BAR, March 1975 and Amihai Mazar, Archaeology of the Land of the Bible (New York: Doubleday, 1990), pp. 495–496. Because the Beer-Sheva altar was dismantled, we don’t know its original measurements and orientation.
We do not count a few rock-cuttings that some scholars, eager to identify “cultic” remains, have defined as altars. See Shmuel Yeivin, “Bamah,” Encyclopaedia Biblica, vol. 2, pp. 149–152 (in Hebrew). In Petra and its vicinity, many rock-hewn altars are known (see Gustave Dalman, Petra und seine Heiligtümer [Leipzig, 1908], pp. 79–82), but they are not relevant here as they belong to another cultural world, that of the Nabataeans in the first century B.C.E and first century C.E.