Two weeks ago I visited the New York Federal Reserve, for a meeting with a high-ranking official in an elegant conference room overlooking Wall Street. It's an appropriate view now, considering that in today's post-crisis world the Fed has assumed oversight responsibility for all the financial markets, not just banks.

Before the meeting above Wall Street, though, I went below Wall Street. I went five stories down into the solid bedrock underneath the New York Fed, 30 feet below the level of the New York subway system and 50 feet below sea level.

There the New York Fed has a vault containing about $300 billion in gold bars.

It's the largest single gold hoard in the world. It holds more than Fort Knox. Almost all of it is held in custody for foreign governments -- very...