During World War I the Romanian government sent some very valuable items over to Russia for safe keeping, this was considered the Romanian Treasure. When it was time to return the treasure part of it was missing. The reason for this was that Bucharest was ruled by Germany during that time and in fear of a German conquest the Romanian government left for Iasi and took the treasure with them.
With the Romanian treasure now abroad many options of where to send it were considered however the risk of German interception was too great. Some thought it best to be sent to the US or to England, others advised that it be sent to Denmark, since they were neutral. The fears of a German victory and the possibility of offending the Russians, the treasure never left Romania.
The Romanian government agreed that they would keep the treasure in the Kremlin until the war ended but instead the treasure was loaded onto a train in 1916 and headed east with what would be worth over $1 billion today. This was only part of treasure, left behind was ancient jewels, antiques, precious artwork, and Romanian manuscripts which left on a separate train several months later. It is possible that the second train could have been more valuable than the first.
Since then not much has been talked about the missing Romanian Treasure besides the fact that it was moved to another location during World War II. The last time it was seen was in 1935 and many of the objects were missing as the treasure had obviously been rummaged through. Many attempts were made by the Romanian government to get the treasure back but they were all unsuccessful. A small portion was returned in 1935 and a bit more in 1956 but the most important part of the treasure was never returned.