The Dendera zodiac is an ancient Egyptian bas-relief from the ceiling of the pronaos of a chapel dedicated to Osiris in the Hathor temple at Dendera.
The chapel was begun in the late Ptolemaic period and its pronaos was added by the emperor Tiberius. Jean-François Champollion dated the relief correctly to the Greco-Roman period, which greatly pleased the Catholic authorities of the time, who feared the antiquity to be over 6,000 years old, and therefore before the accepted biblical date of Creation. The now-accepted date for the relief is 50 BC, since it shows the stars and planets in the positions they would have been seen at that date.
What you see today at its original place is a cast. The authentic Dendera zodiac is now on display at the Musée du Louvre, Paris.
Sharon Waxman describes the removal of the Dendera zodiac in her book "Loot:The Battle Over the Stolen Treasures of the Ancient World": "The engineer Lelorrain had forged special tools in France to do the deed. Working on the rooftop of the Denderah temple, Saulnier hacked and gouged at the zodiac ceiling over the course of twenty-two days, trying to drag it down using chisels and saws. But when more than three weeks of hacking did not succeed in removing the ceiling, Lelorrain turned to gunpowder in specially drilled holes to dislodge it. The explosions finally did the trick, destroying a nearby sculpture of Isis."
The Dendera zodiac is a planisphere or map of the stars on a plane projection, showing the 12 constellations of the zodiacal band forming 36 decans of ten days each, and the planets. These decans are groups of first-magnitude stars. These were used in the ancient Egyptian calendar, which was based on lunar cycles of around 30 days and on the heliacal rising of the star Sothis (Sirius).
The celestial arch is represented by a disc held up by four pillars of the sky in the form of women, between which are inserted falcon-headed spirits. On the first ring, 36 spirits symbolize the 360 days of the Egyptian year.
On an inner circle, one finds constellations, showing the signs of the zodiac. Some of these are represented in the same forms as their familiar names (e.g. the Ram, Taurus, Scorpio, and Capricorn, albeit most in odd orientations in comparison to the conventions of ancient Greece and later Arabic-Western developments), while others are shown in a more Egyptian form.