Blue Hole (Castalia)
The Blue Hole captured the public’s interest because of its size, about in diameter, clarity, vibrant blue hue, and enigmatic "bottomless" appearance. Contrary to prevalent belief, the depth of the Blue Hole is not unknown, but has been sounded and found to be about deep. Water temperature is about throughout the year. Floods and droughts have no effect on temperature or water level. The Blue Hole is fed by a passing underground stream which discharges of water daily into Sandusky Bay to the north, feeding into Lake Erie. The water contains lime, soda, magnesia and iron, and because the Blue Hole is anoxic, it cannot naturally sustain fish. The surrounding terrain is developed on limestone bedrock and exhibits karst topography due to dissolution of the limestone by ground water, creating water-filled sinkholes. The Blue Hole was known to American Indians and was first recorded in history in 1761. Several similar blue holes are known to local residents. The Blue Hole that once was a tourist attraction is now off limits to the public. It is located on the grounds of Castalia Trout Club. It is to be distinguished from another hole similar in size and eerie bluish-green color. This latter hole is owned by the Castalia State Fish Hatchery operated by the Ohio Department of Natural Resources, Division of Wildlife and is open for public viewing.
Blue Line (CTA)
The O'Hare Branch is the longest section of the Blue Line () and comprises both the oldest and newest segments of the entire route. The line starts at O'Hare International Airport in an underground station below the main parking garage, servicing Terminals 1, 2, and 3. The line emerges in the median of the O'Hare main access road (Interstate 190) just northwest of Terminal 5, about a mile (1.6 km) west of Mannheim Road. The line runs in the median of Interstate 190 east through Rosemont. The line has a stop at River Road in Rosemont, which is also the location of one of the line's two storage yards, then tunnels beneath the Kennedy Expressway/Northwest Tollway interchange near the Des Plaines River. The line runs in the median of the Kennedy Expressway (Interstate 90) until a point southeast of Addison Street. South of Addison Street, the line exits the freeway and enters a subway under Kimball Avenue. The line travels under Kimball Avenue and Milwaukee Avenues through Logan Square. South of Logan Square, the line emerges above ground onto an elevated structure parallel to Milwaukee Avenue. This section of structure, built in 1895 as part of the Metropolitan Elevated's Northwest Branch, is the oldest portion of the Blue Line, and the sole section of the line on an elevated viaduct. The three stations on this section (California Avenue, Western Avenue, and Damen Avenue) are also the only three stations on the line to use side platforms instead of island platforms.