According to Wikipedia, Empress Cixi embezzled 30 million taels of silver from the modernization of Qing Navy to build the Summer Palace. What is 30 million taels of silver equivalent to in modern USD? Was the Summer Palace funded entirely by navy funds, or did it cost even more?
With a little research: 1 Tael is equivalent with 37.5 or 33.9 or 37.8 g of silver, depends on region where it was issued.
Let's do the math: 30 million of taels are between 1017000 and 1134000 kilograms of silver. The wikipedia doesn't say the purity, but I found an another source from JSTOR which declares it was pretty pure, between .944 to .989 so if we count with 96% of the silver value, it will be accurate. The final lower sum is: 690 USD x 1017000 = 701 million USD, the higher is 690 USD x 1134000 = 782 million USD.
It is a huge sum of money with physical value today.
Take a note: this estimation is roughly implemented into current currency system. The value itself depends on current price of silver, which worth less compared to gold today than it worth several hundred years ago, so the actual objective value can be different.