Greece sits at the southern tip of the Balkan Peninsula in southeastern Europe. It is surrounded by the Mediterranean Sea on three sides. The country includes about 6,000 islands, though only about 200 of them have people living on them. The islands were formed millions of years ago when parts of the land sank beneath the sea, leaving mountain peaks poking above the water. The Greek landscape is mostly rocky and mountainous. Mount Olympus, the tallest peak, rises 9,570 feet above sea level. Ancient Greeks believed their gods lived on top of it. Because of the rocky terrain, only about 20 percent of Greek land can be used for farming. Olives, grapes, and wheat grow best in the warm, dry climate. On March 25, 1821, the Greek people began fighting for independence from the Ottoman Empire. The Ottoman Turks had controlled Greece for nearly 400 years. Greeks throughout the country rose up in rebellion. After years of fighting and help from Britain, France, and Russia, Greece won its freedom in 1829. Today, March 25 is a national holiday. Parades fill the streets, and Greek families gather to celebrate their heritage with traditional food and music.