Mosques, madrasas, tombs, palaces, hammams (public baths), Sufi hospices (e.g., khanqahs or zawiyas), fountains, sabils, commercial structures (e.g., caravanserais and bazaars), and military fortifications are all common or major forms of buildings in Islamic architecture. The four most important types of Islamic buildings are mosques, madrassas, tomb buildings, and hospital/charitable institutions. These are the most common types of buildings found in Islamic countries. However, many other kinds of buildings exist in both rural and urban areas; for example, houses, schools, shops, churches, synagogues, museums, libraries, towers, bridges, and dams are all commonly found structures in Islamic societies. Even oil wells and irrigation systems have been built by Islamic architects. The variety of building types found in the Islamic world demonstrates the diversity of ideas and styles present during this time period. In conclusion, Islam has had a significant impact on the design of buildings throughout the centuries. Islamic architects have devised various techniques and materials that are still used today in some buildings around the world.