facing east

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​There is ancient symbolism involved in praying this way and in seeing the sun as a symbol of Christ and the new messianic day that has dawned with His Incarnation. Churches were traditionally built facing East, whence the sun rises and whence Christ is traditionally expected to return at His Second Coming. -explanation provided by catholiccompany.com

So, in the traditional Latin Mass, priest and followers face in the same direction toward God, the Crucifix, and we see the priest's back because he is not our focus.
https://www.fssp.org/en/find-us/where-are-we/​

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