The Swiss Central Bank - National Bank of Switzerland - is unusual in several respects.
It is controls that country's currency, the Swiss (CHF) Franc but the bank is a privately owned entity.
However it is the banks investment strategy which is of real interest, because every quarter it publishes updates about it's own financial performance and what it has invest in and divested from.
The Swiss Central Bank has acquired vast shareholdings in Apple, Facebook, Amazon, Microsoft.
The fact that each central bank can literally print it's own money, means that that money has to be housed somewhere
In the case of the Swiss Central Bank some of that printed money is being invested in shares in companies based outside Switzerland.
The size of the balance sheet for the Swiss Central Bank is $840 billion. That's 127% of Switzerland's annual GDP.
Other central banks such as the Fed are nowhere near that size compared to the size of their respective national GDP's.
Good article hearing highlighting some of the issues