The cornerstone is the principal stone around which construction in antiquity was achieved. In the lexicon of biblical images of architecture, no image is more evocative than the cornerstone, the focal point of a building, the thing on which it most depends for structural integrity. Thus early in the catalog of God’s acts of creation in Job 38:6, the divine voice from the whirlwind asks regarding the world, “Who laid its cornerstone?” (Ryken, Leland et al. The Dictionary of Biblical Imagery. 2000: 166. Print).There are repeated references to Jesus as the cornerstone rejected by the builders. Paul explains that Christ Jesus is the chief cornerstone of the church which is built upon the foundation of the apostles and prophets (Ephesians 2:20). This concept is the fulfillment of Old Testament prophecies (1 Peter 2:6; Psalm 118.22; Matthew 21:42; Acts 4:11, et al. The Louw-Nida Lexicon says the Greek word used in these texts refers to “The cornerstone or capstone of a building, essential to its construction – ‘cornerstone, important stone.” I notice that several sources use the term capstone. I have seen these capstones at the top center of an arch used in the construction of an entry arch to a large building. Without the capstone the arch would soon fall.
One of the largest cornerstones of the Temple Mount enclosure wall. This is the area of Robinson’s Arch.Wiemers describes the large cornerstone pictured above:
A very large corner stone with margin and boss, located on the southwest corner of the Temple Mount. This southwest corner has some of the largest ashlar stones of the entire Temple Mount complex, measuring 39 feet 4 inches long by 7 feet 10 inches wide and 43 inches high. The large stone shown here is called the master course stone and weighs about 80 tons. All these stones form a strong corner as they alternate back and forth as headers and stretchers all the way up. The larger stones helped stabilize the smaller stones stacked below. (Wiemers, Galyn. Jerusalem History, Archaeology and Apologetic Proof of Scripture. Waukee, Iowa, Last Hope Books and Publications, 2010, p. 105.)We noted earlier that several sources suggest the Greek word for cornerstone could also describe a capstone. I have seen several of these capstones used in arches. The next photo shows an example from Patara (Acts 21:1; now in Turkey). It is a triple-arched gate. For more information see Wilson, Biblical Turkey. The capstone may be seen above each of the arches, but is especially noticeable above the center arch. These capstones are not just for beauty; they are essential to hold the arch together.