There are no central exchange headquarter for foreign exchange because it is an open market where dealers negotiate their own price feeds through proprietary platforms. The main geographic trading center however, is in London, followed by New York, Tokyo, Hong Kong and Singapore.
Foreign exchange banks throughout the world participate and play a big role in forex, although their roles have been greatly reduced from yesteryear. John Atkin points out in his book The Foreign Exchange Market Of London that "The Bank had long used a mixture of nods, winks and arm twisting to influence the behavior of participants in the domestic money and banking markets." It is no secret that Foreign exchange banks dominate the top level of access for the best Forex spread. Using their big pool of clients along with their own accounts, inter-bank market made up more than half of all Forex transactions.
In the late 1930's banks were the market maker for specified currencies. According to Atkin, "In the case of the US dollar / sterling rate, the Bank announced - when the market re-opened on 5 September 1939 - that its buying rate for dollars would be $4.06, and that its selling would be $4.02. This spread of 4 US cents or 400 points, compared with a normal peacetime inter-bank spread of 13 points, or less." His observation serve to highlight the profitable spread enjoyed by banks in that era. This trend continued until after World War II, when a normal foreign market exchange market slowly became apparent.
Banks do not have total control over foreign exchange rates as they fluctuate according to as actual monetary flow, budget, trade deficits, changes in GDP growth and interest rates and other economic conditions. In foreign exchange platforms, virtually everyone get access to major news at the same time, and banks are no different. Nevertheless, banks still gain the upper hand from monitoring the trend of their customers' order flow.
Apart from normal banks, central banks also participate in the foreign exchange market to regulate currencies in protection of their economy.Central banks or and national banks serve a dominant role in controlling inflation, interest rates and money supply. Since a country's currency rates have direct implications on it's economy through the trade balance, almost all central banks tend to intervene to influence the value of their currencies. This is known as managed float.
Central banks can determine foreign exchange rates to a certain extend, as they have huge foreign exchange reserves in hand to stabilize the market. Again, this does not always work as the combined resources in the actual market usually have a bigger say. As highlighted by William P. Osterberg in his article 'Why Intervention Rarely Works' in year 2000, "foreign-exchange-market intervention is generally ineffective when undertaken independent of monetary policy." An example of central banks' limitations are evident in the 1997 Southeast Asia economic crisis when the International Monetary Fund (IMF) failed to prevent currency depreciation.