The city of Windsor is laid out along the banks of the Detroit River. Unlike many cities, Windsor did not grow from a central downtown core but was instead the product of the amalgamation in 1935 of the four distinct communities of Windsor, Sandwich, Walkerville, and Ford City (later East Windsor). Additional territory was annexed in 1966. The current city of Windsor covers a land area of 120.3 sq km (46.4 sq mi). The Windsor census metropolitan area (CMA), which consists of the city of Windsor and ten other municipalities, covers a land area of 861.7 sq km (332.7 sq mi). Most of Windsor's retail shopping areas are centered outside of the city's downtown area, primarily at Devonshire Mall in the west central suburbs. Windsor's downtown area is the administrative center of the city, where City Hall and City Hall Square are located. The downtown also contains several fine historic buildings, including the Duff-Baby House, a large manor dating from 1798. Other buildings are Willistead Manor, a large mansion that was completed in 1906, and Mackenzie Hall, which was built in 1855 by the second prime minister of Canada, Alexander Mackenzie, and is now an arts center. Points of interest in the city include the Cleary International Centre, a convention center located on Windsor's waterfront, and Dieppe Gardens, a waterfront park in the downtown area. Other sights are the Canadian Club distillery, which offers guided tours; Coventry Gardens, which is home to the Peace Fountain and is located along the river on the city's eastern edge; and the Ojibway Nature Centre, which is in the western part of the city. The new Casino Windsor, a complex of gambling halls, restaurants, bars, and a 21-story hotel, was completed in 1998. Windsor has been a base of American automobile companies from the beginning of the 20th century and it remains a major center of auto industry employment and manufacturing. The Ford Motor Company built an auto manufacturing plant in Windsor in 1904. Ford was followed by Chrysler (now part of DaimlerChrysler AG) and General Motors Corporation, which built plants in the 1920s, and by several smaller companies such as Studebaker and Packard. DaimlerChrysler is now the city's biggest employer, with over 8,000 employees. Other major employers in the city include the H. J. Heinz Company, which processes farm products from the agriculturally rich land outside of the city, and Hiram Walker and Sons Limited, makers of Canadian Club whisky. Additional manufactures in the city include salt, metal products, plastics, high-tech equipment, machinery, and pharmaceuticals. The most significant new stimulant to the local economy is Casino Windsor, which opened in 1994 and moved to its permanent home in 1998. The operators of the casino claim that they provide 15,000 direct and indirect jobs to the city. The casino has also increased tourist traffic to Windsor. Windsor has many transportation links. It is one of the busiest ports of entry into Canada and is connected to the city of Detroit, Michigan, by the Ambassador Bridge and by the Detroit-Windsor Tunnel. Windsor is located at the end of the Macdonald-Cartier Freeway, which connects the city with Toronto, Ontario, and Montréal, Québec. The city is also served by several rail lines and provincial highways, as well as Windsor Airport. The Detroit - Windsor Tunnel is the only vehicular international sub aqueous border crossing in the world. It has been recognized as one of the great engineering wonders of the world and is the second busiest crossing between the United States and Canada. Located between Detroit, Michigan and Windsor, Ontario, connecting the US Interstates to Ontario’s Highway 401, it is one of the fastest links between Ontario and United States. The Detroit - Windsor Tunnel crossing is a large complex consisting of toll and inspection plazas on each side of the border where you pay for your crossing and intermingle with inspection agencies such as Immigration and Customs. The Tunnel is 5,160 feet long (1,573 meters) with a height clearance of 13 feet 2 inches ( 4 meters ) . The roadway is 22 feet wide ( 6.7 meters ) and allows for two lanes of traffic in opposite directions. First opened to traffic on November 3, 1930, construction took 26 months and cost $23,000,000. The maximum depth of the roadway beneath the river surface is 75 feet ( 22.8 meters).