Frankfurt is Germany's international center for finance and trade, located in the heart of Europe. As a major transportation hub with Europe's largest airport, Frankfurt is an important city for international business. Over 200 banks and prestigious financial institutions are headquartered in Frankfurt, along with the European Central Bank and other regulatory authorities. The Opernturm building in Frankfurt's financial district houses over 2,500 workers and utilizes environmentally friendly construction techniques. It provides easy access to the city's public transportation system and nearby hotels.