There are more than 150 000 amazing Thracian mounds built for three and a half millennia. Most of them hide temples under them and are unparalleled creations with their beautiful columns, monolithic construction, fine friezes and solidity. The painted images on their vaults are evidence of the mastery of the painters. Although they have been underground for over three millennia their frescoes haven't lost their colours because the colour makers have had sound knowledge of the substances which they have mixed for the plaster.