Sauron's temple was the common name given to the Temple of Melkor constructed late in the Second Age in Armenelos at the behest of Sauron.

The temple was round, 500 feet in diameter, with walls 50 feet thick, and a silvered dome. At the center of the temple was an altar of fire whose first burning was the wood of Nimloth, the White Tree of Númenor.

Human sacrifices to the honour of Melkor were also made in Sauron's Temple At first the sacrifices came mostly from the Elendili but as time went on, captured prisoners from Middle-earth were also sacrificed, all in the hope of Númenorians being granted the gift of eternal life by Melkor.

Smoke fire and bloodletting continued almost unceasingly in the temple right up until its final destruction in the Downfall of Númenor
Encyclopedia entry originally written by PotbellyHairyfoot