We hosted an exchange student from near Stuttgart, Germany, for a year in the US. A year later, I was able to visit her family in Germany. Her father is a civil engineer for Stuttgart Airport, and he told me about how they still harvest huge ice pieces from the winter in nearby lakes, and store them in caves near the airport for natural cooling. In the winter, the heat from their computer server rooms of the airport is spread throughout the airport, rather than heat directly from fossil fuels.