The Toronto Dominion Centre is the most distinctive set of office towers in the city’s financial district. Three of the five black buildings were designed by Mies van der Rohe and built in the late 1960s. So was their air conditioning.

The three original towers, which contain about 3 million square feet of office space, were among the first buildings connected to Toronto’s Deep Lake Water Cooling System in September 2004, saving the local electric utility 7.5 megawatts of electrical demand every working day.

[Read](http://www.csmonitor.com/2007/0830/p13s01-stgn.html “Read the Story”) (Christian Science Monitor)