Seven locks and seven keys
On such a ceremony where the Czech Crown Jewels are used, each one of the chambers' seven keyholders must attend to open the chamber. The keyholders of the Crown Jewels are important members of state, for example, Czech Republic's President, the Prime Minister, and the Prague Archbishop.
If you aren't in Prague during one of the momentous exhibitions when the jewels are unlocked, you can view their replicas in Lobkowicz Palace (in Prague Castle) or in Karlštejn Castle.
And they say that the crown is cursed. Every person other than the king will die if he put on the crown.