The headquarters of GATT is located in Geneva, Switzerland.

GATT stands for General Agreement on Tariffs and Trade. It was signed in 1947 and came into effect in 1948. The main goal of GATT was to reduce trade barriers between countries such as customs duties and import quotas. This helped promote international trade and cooperation after World War II.

GATT provided a platform for countries to negotiate trade deals and settle disputes related to international commerce. Over the years, many countries joined GATT and worked together to make global trade smoother and fairer.

Geneva was chosen as the headquarters because it is a well-known center for international organizations and diplomacy. Many global institutions such as the World Health Organization and the United Nations also have offices in Geneva. The city is neutral and respected for hosting important international discussions.

In 1995, GATT was replaced by the World Trade Organization (WTO), which continued its mission with more power and structure. The WTO also has its headquarters in Geneva, continuing the work started by GATT.

So, the correct answer is Geneva.