Described as the eighth wonder of the world by those who saw it, the Amber Room is certainly the most unique missing treasure in history.

It was an 11-foot-square hall consisting of large wall panels inlaid with several tons of superbly designed amber, large gold-leaf-edged mirrors, and four magnificent Florentine mosaics. Arranged in three tiers, the amber was inlaid with precious jewels, and glass display cases housed one of the most valuable collections of Prussian and Russian artwork ever assembled.

Created for Prussia's King Friedrich I and given to Russian czar Peter the Great in 1716, it was located at Catherine Palace, near St. Petersburg. Today, the Amber Room would be valued at more than $142 million.

When Adolf Hitler turned his Nazi war machine toward Russia, the keepers of the Amber Room got nervous. They tried to move it, but the amber began to crumble, so they tried to cover it with wallpaper. They were unsuccessful and when the Nazis stormed Leningrad (formerly called St. Petersburg) in October 1941, they claimed it and put it on display in Königsberg Castle during the remaining war years.

However, when Königsberg surrendered in April 1945, the fabled treasure was nowhere to be found. The Amber Room was never seen again. Did the Soviets unwittingly destroy their own treasure with bombs? Was it hidden in a now lost subterranean bunker outside the city? Or was it destroyed when Königsberg Castle burned shortly after the city surrendered?

We'll probably never know for sure. But fortunately for lovers of opulence, the Amber Room has been painstakingly recreated and is on display in Catherine Palace.