Great Blue Hole
The Great Blue Hole is a giant marine sinkhole off the coast of Belize. It lies near the center of Lighthouse Reef, a small atoll from the mainland and Belize City. The hole is circular in shape, across and deep. It was formed during several episodes of quaternary glaciation when sea levels were much lower. Analysis of stalactites found in the Great Blue Hole shows that formation took place 153,000; 66,000; 60,000; and 15,000 years ago. As the ocean began to rise again, the cave was flooded. The Great Blue Hole is a part of the larger Belize Barrier Reef Reserve System, a World Heritage Site of the United Nations Educational, Scientific and Cultural Organization (UNESCO).
O'Hare station
O'Hare is the 'L' station at the northwestern terminus of the CTA's Blue Line. It is a subway station with two island platforms serving three tracks, located at O'Hare International Airport, 17 miles (27 km) northwest of the Chicago Loop. The station is located underneath the O'Hare parking garage. Trains are scheduled to depart from O'Hare roughly every 2–7 minutes during rush-hour periods and take about 40 minutes to travel to the Loop. It is the westernmost station of the 'L' system. It is also the only station without coordinates in Chicago's grid system, as O'Hare lines up with no street in the city. It is the only underground terminus, the only terminal where a premium fare applies, and is the only terminal that does not directly connect to any CTA or Pace buses. It is also one of two terminals (the other being Dempster-Skokie on the Yellow Line) that does not have a yard assigned to it (the yard is located at Rosemont, one stop east).