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Environmentalist Dhruv Boruah cycles on London's waterways collecting trash and raising awareness about plastic pollution.

Dried pools of molten aluminum dot the charred roads of a small Greek village ravaged by fire this week. The flames were so hot that cars in their path began to melt, metal dripping to the ground and tires turned to liquid rubber.

Dozens of people have been killed and scores injured in the worst wildfires to affect Greece in over a decade.

At least 74 people have died in the worst wildfires to hit Greece in more than a decade, with some residents forced to flee into the sea to escape the advancing flames.

View CNN's Big Ben Fast Facts and learn more about the clock and bell in Elizabeth Tower.

Read CNN's Summer Olympics Fast Facts to learn more about the athletic competition.

At a press conference with Secretary of State Mike Pompeo, Secretary of Defense James Mattis said Iran has a destabilizing influence in the Middle East and must "shape up and show responsibility."

Read CNN's Fast Facts and learn more about the Eiffel Tower in Paris.

The summer of temperature extremes just keeps going, with record heat waves this month on all four continents that occupy the non-tropical Northern Hemisphere where it is now summer.

With exactly two years to go until the Tokyo 2020 Olympics, Japan continues to swelter under searing heat.