Breathtaking images of the northern lights in Denmark

This is a list of the most populous cities in the world, defined based on 2018 United Nations estimates, official census estimates, and the 2021 "Demographia World Urban Areas" report.

"World Urbanization Prospects," a publication by theONU, defines the population of a real city as "the population living within the administrative boundaries of a city." For many of the metropolises, however, the metropolitan area is administratively distinct from the urban agglomeration proper. For this reason, ONU recent estimates distinguish three definitions of cities: cities proper, urban areas and metropolitan areas.

According to the definition of "city proper", based on administrative uniqueness, the Chinese city of Chongqing is the largest in the world.

According to the other two definitions, Tokyo, despite being divided into several administrative units, is the most populous "urban agglomeration" (i.e. the agglomeration without rural areas) in the world, while the Chinese city of Shanghai is the most populous "metropolitan city" (i.e. the area interconnected by common infrastructure and frequent transport).

The data in this gallery include the total population of agglomerations in their highest estimates, thus also including metropolitan areas.

The lonely house on the Icelandic island of Elliðaey has generated numerous theories and speculations, including a refuge for billionaires in the event of an apocalypse or the abode of a religious fanatic.

However, these stories have been disproved. The real story behind the isolated mansion dates back to the 1950s, when it was built by the Elliðaey Hunting Association as a refuge for puffin hunters. The island of Elliðaey, uninhabited for about 90 years, is an ideal nesting habitat for these endangered birds.

Environmentalists visit the island and use the lodge to monitor and protect puffins during their summer breeding season.

The sequoia National Park is one of the true treasures of Sierra Nevada, California. However, this corner of paradise is threatened every year by fires, which increasingly ravage huge areas of land. It is estimated that 20 percent of the park has been destroyed in the past three years by fire. U.S. firefighters have therefore initiated an action aimed at decreasing the risk of fire in the area, paradoxically using fire.

Prescribed fire is a technique used since the mid-twentieth century, whereby certain particularly flammable areas, such as dry shrubs for example, are set on fire to prevent any fire from spreading uncontrollably.

This technique is now widely used, but it takes tremendous preparation and experience to safely put it into practice. Impressive photos of the redwood forest, where the grandeur of the trees makes everything very striking and fascinating.

A forlkift driver in China had a day to forget when he accidentally dropped an oven on the bonnet of a parked Ferrari F8 Tributo. 

Pictures and video footage have surfaced on the net, showing a professional oven resting on the bonnet of the Italian supercar. Although the extent of the damage is unknown, the bonnet and front bumper are likely to require extensive repair work. 

It is believed that the accident occurred when the forklift driver was attempting to drive around the front of the parked supercar and its load became unbalanced. Although forklift accidents are not uncommon, this accident is particularly embarrassing given the expensive vehicle involved.

A prestigious American university conducted an in-depth study that showed how New York, and specifically the island of Manhattan, is sinking into the ground at a rate of about 1-2 millimetres every year.

The entire area was completely mapped by comparing satellite data with subsurface geology models. In the long term, this geological trend could increase the risk of flooding caused by rising river levels.

The city's subsoil is in fact mostly made up of sand, silt, clay sediments and rock outcrops, and the enormous weight of the buildings is starting to become a problem.

A literally unbelievable discovery comes from South America, and specifically from the territories that once belonged to the Mayas, one of the three great pre-Columbian civilisations along with the Incas (Peru) and Aztecs (Mexico). In the territory between present-day Guatemala and Mexico, in fact, a huge network of highways has been discovered.

The complex of roads and bridges dates back as far as 3000 years, and the team of scientists who made the discovery compared it in importance to the discovery of the Egyptian pyramids. It is estimated that the 'highway' continues for hundreds of kilometres and intersects some 417 ancient Maya settlements.

For this discovery, a new technology called lidar was used, an advanced type of radar that reveals presences hidden by dense vegetation, resulting in 3D reconstructive images.

Truly incredible are the photos coming straight from Iceland, where the volcano called Litla-Hrú has suddenly started erupting. The huge mountain is located only 50 km from the nation's capital, the city of Reykjavik.

Local authorities reported that the eruption appears to have started around 4.40 p.m. on 10 July, from the north side of a small mountain called Litla Hrú,t and the crack is believed to be about 200 metres long. At the moment, no problems for air traffic have been reported.

Iceland has as many as 100 volcanoes on its territory between active and inactive. The entire island can be regarded as one enormous volcano. The photos coming straight from the spot are truly unbelievable.

Forestry officials in parts of Germany are observing an increase in bark beetle populations due to the recent unusually dry and warm weather in May and June.

Areas in Saxony, Bavaria and Baden-Wurttemberg in particular are affected. Bark beetles are beetles that penetrate the bark of trees and block the necessary circulation of water and nutrients, thus devastating the forests.

For experts, this is a real calamity, which is getting worse every year since 2018.

Very ugly event occurred on the morning of July 12 in Naples, Italy. A fire, which broke out in the early hours of dawn, completely incinerated the "Venus of Rags," the work of contemporary art created by Michelangelo Pistoletto.

The work had been unveiled on June 28 and represented "the humanity of today, called to express its best side," to quote the words used by the artist himself.

The burning obviously melted the statue and destroyed the clothes and rags that adorned it. The origin of the fire is not yet known, but arson is speculated.

The rags symbolized waste or refuse, which Venus has the power to regenerate.

Incredible crash for a Ferrari 360 Challenge in Australia. The crash cost the driver behind the wheel of the rare car that was destroyed in Melbourne, where fortunately there were no injuries, but the $600,000 supercar was devastated. 

The crash of this Ferrari 360 Challenge was documented in a video showing the Italian supercar crashing into two cars stopped in the oncoming lane.

The video is making the rounds on the web and shows how the driver lost control of the rare car due to high speed.