According to Inverse, ancient Roman architects discovered that the less exposure streets and alleys have to the sun, the cooler a city is. This is probably one of the main reasons why cities such as Rome have many narrow streets, which may be difficult if not impossible to navigate with a car, but provide a breathing space in the scorching days.

This also comes in contrast with the way Eastern European cities have been developed in the past decades during the communist regime, with large spaces between apartment and administrative buildings, usually filled with trees.

Back to the past, however, Greek architects took things one step forward and painted all buildings white, both the walls and the roofs, so they could reflect as much of the heat as possible.

Centuries later in the US, Thomas Jefferson proposed a different cooling solution for cities located in southern states, such as Louisiana or Georgia, which experienced not only high temperatures, but also increased humidity. Because the number of buildings and their sizes were larger than those built in antiquity, he thought of implementing green spaces in between densely-constructed areas, allowing cool and warm air to move better, similar to how urbanists planned cities in Eastern Europe.

The drawback of this second approach is what led to today's unbearable heatwaves. Whenever trees fall or real estate companies get their hands on an empty lot, they fill it with an apartment or office building, usually made from materials that trap heat or reflect it on the citizens. This can't happen in cities like Rome, for example, because there simply isn't space for this kind of a development on most streets.

The amount of concrete and asphalt from buildings, streets and parking lots amplifies the heat significantly, especially on large boulevards. This leads to another problem, the use of air conditioning, which also releases heat through the external units, increasing the temperatures in the process.

The effect is that on a summer afternoon, temperatures in a city can rise between 5 to 11 degrees Celsius, a serious health risk for anyone who doesn't have access to air conditioning or who happens to walk on the street at that time.

What can cities do now to keep their cool in the future

But not all is lost, as there are still things that urban settlements can do to lower their climate impact. First is lowering the energy usage across all sectors, including transport, industries and powering the buildings, since urban areas account for 70% of the energy-related greenhouse gas emissions globally.

Planting trees will also have a huge impact for the cities that want to lower their temperatures and some experts say that using only half of the available space for planting can lead to a decrease of 2.8 to 5.6 degrees Celsius in the ambient temperature.

Painting the buildings and their roofs in light colors also has important benefits, as proven by Greek cities, which is why more urban settlements are requiring new constructions to be painted lightly. This includes Los Angeles, which in 2013 became the world's first major city to require all new buildings have lightly-colored roofs.

The citizens can always get involved, even indirectly, by electing mayors who value, plan and implement climate strategies that will benefit these areas in the long run.