The Salt Lake Temple Star Stones
There are three different types of five-pointed star stones on the Salt Lake Temple. There is an upright star stone over each of the arched windows. There is an upside-down star over the arch of each doorway. There is also a row of star stones at the top of each tower on the East face of the temple. These star stones have several symbolic meanings, but the meaning all of them have in common is that all act as a reminder to watch the stars in the heavens for the signs of the Second Coming of Jesus Christ. (Luke 21:25)
The star stones on the keystones over the arched windows represent the glory of God, and the pillars of heaven. The pillars are those that receive eternal life in God's kingdom (Revelation 3:12). These star stones are also symbols of the Telestial Kingdom, which in LDS theology is the Third and Lowest Kingdom of Glory.
The inverted stars on the keystones over the temple doors represent The Morning Star, which is the brightest star in the night sky. The Morning Star was used by travelers to find their way in the night and to navigate their path. In Revelation 22:16, Jesus Christ refers to Himself as The Morning Star. So the upside-down stars are actually symbols of Jesus Christ and represent Him being our path to salvation and exaltation in God's Kingdom. The star pointing downward represents the light of God's truth shining down on us from Heaven.
The large upright star stones on the East towers represent people. They're placed on the East towers, which represents the Melchizedek Priesthood, to symbolize the need for people to attach themselves to the Holy Priesthood of God so they can receive the power and blessings of God which are bestowed through the sacred ordinances of the temple. Stars are also a symbol of the Abrahamic covenant, which also pertains to the blessings of the temple.