Deloitte published their assessment of Rome's 2000 year-old Colosseum, which could well cost from $250 million to $1 billion to build today.  You can  read the details here , but, ta-da, it is worth $79 billion.  It would rank   #14 in the current list of world billionaires . There are moments and experiences, says Mastercard, that are priceless, but many famous historical artifacts are also in that category, especially those of Leonardo da Vinci. Some of his works do have known values.  A prominent one, and most expensive art piece ever sold, is  Salvator Mundi,  which was bought by the Crown Prince of Saudi Arabia Mohammed Bin Salman in 2017 for $450 million, some say as a gift to the Louvre Abu Dhabi, and today has a value closer to $500 million, or half a billion dollars. To the right is how the Leonardo pictured Jesus Christ, but it is still not clear if he finished it in the 1490s while working in Milan on  The Last Supper , or in Florence a...