Are there any unknown Archaeological sites like the holy grail, or crystal skulls, in the world?

This was a really hard question to word but I was wondering if there was any items in the world that are talked about but not proven to exist such as the holy grail, or ark of the covenant? Yes those are in the Indiana Jones Movies. All these items have been talked about like a legend. I was just wondering if there are other things in the world talked about in literature around the world, or in Ancient history that are like these items.