Rubik's Cube is considered to be the best-selling toy in the world with more than 350 million sold worldwide.
During the peak of the toy's popularity in the mid-1980s, the company estimated that one-fifth of the world's population was trying to get it.
The most expensive ruby cube is made of 18 carat gold, with each panel having 25 valuable stones. It has amethysts, emeralds, sapphires and rubies.
The price is $ 2.5 million.
