According to Wikipedia:
The Rat Hole was a 2-lane tunnel constructed in 1927 and traversed north-south under present day 109th Street between 104th and 105th Avenue, in the northwest corner of Downtown, in Edmonton, Alberta, Canada. It was 168 metres in length, 3.3 metres in height, and constructed to accommodate automobile, bicycle and pedestrian traffic.
The City of Edmonton proposed for the construction of a tunnel/underpass in 1926 to burrow under a span of 22 railway tracks in the old Canadian National Railway yards. A call for tenders was put out in the following year, 1927, with seven businesses bidding for the contract, out of which, Jamies Construction Co. Ltd. received the contract from city engineer A. W. Haddow to construct the tunnel.
The 109 Street Subway, the original name of the tunnel, was officially opened by then Mayor Ambrose Bury on October 19, 1928. An Edmonton alderman later coined the name “Rathole” for the tunnel.
In 1957, a transportation study recommended the construction of a parallel subway to improve the traffic flow. However, in lieu of this recommendation, in 1960 the city constructed an overpass along 105th Street over the CN rail tracks.
The tunnel was susceptible to seasonal flooding, and proved hazardous because of its low clearance and visibility upon entrance and exit. There were also safety issues concerning pedestrian usage of the tunnel.
The tunnel remained opened for 73 years, during which, as many as 27,000 cars passed through daily.
In January 2000, the city tendered the project for the demolition of the tunnel and conversation of the area into a divided highway. Standard General Inc. was awarded Prime Contractor for the project.
The project began in April 2000, at which time, there were concerns of inconvenience during the scheduled 4 months for the project. City transportation engineers managed to complete the project 3 weeks ahead of schedule without compromising safety, environmental, and budgetary concerns. This was accomplished by beginning demolition of the tunnel from the north end instead of taking the entire tunnel out at once. Concrete removed from the tunnel was recycled and used in the fill.
On July 4, 2000, the Rat Hole, reopened as a 6-lane divided highway that now runs along 109th Street between 104th and 105th Street, generated much public interest at the time.
In 2002, the project was awarded the American Public Works Association Project of the Year Award, the first time the award was won by a Canadian firm of consulting engineers.
(These ratty caches are located in a Cook County Forest Preserve known as Sandridge Nature Center. The hours if operation are 8:00 am to 4:30 pm daily from March through October and 8:00 am to 4:00 pm daily November through February. The nature center is CLOSED on Thanksgiving Day, Christmas Day, and New Year's Day.)
* Please note . . . No pets are allowed.