Athens' new mayor will plant 25,000 trees over the next five years to try to cool the sprawling Greek capital, he told AFP. Scorching summer heatwaves can make the city of tightly-packed concrete office and apartment blocks almost unbearable, with temperatures topping 40 degrees Celsius (104 Fahrenheit).To make matters worse, nearly a quarter of the trees on the mountains surrounding the capital have been lost to forest fires over the past six years, the mayor said.