6 Dinosaur footprints in Plagne, France.

In 2009, near the southeastern city of Lyon on the Jura Plateau in a tiny French village known as Plagne, amateur fossil hunters discovered the largest footprints found so far in the world.

The footprints are an amazing 1.2 to 1.5 meters (3.9 to 4.9 feet) wide. According to the paleontologists at the National Center for Scientific Research (CNRS), this size corresponds to animals that weigh over 30 or 40 tons.

The footprints are preserved in dried, chalky sediment dating back 150 million years ago to the Upper Jurassic Period. Though these certainly are very big, the footprints might not belong to the biggest dinosaur there ever was.

The biggest is a creature known as Amphicoelias fragillimus from the sauropod (the big long-necked, long-tailed herbivore) family believed to weigh at least 122 tons and measure 130 to 200 feet long. (source)

7 The longest escalator in the US.

Opened in 1990, Maryland’s Wheaton Station is the second deepest station after the Forest Glen Station which is in Maryland as well. The station boasts the longest set of single-span escalators that are 70 meters (230 feet) long and reach a height of 35 meters (115 feet).

It takes approximately two minutes and 45 seconds to take travel on it in one direction. To save expenses while building at such a depth, the station features a separate platform and tunnel for each direction, similar to London Underground’s tube stations. (source)

8 This great big circle is the event horizon of the third-biggest, supermassive black hole. That tiny thing at the center is our Solar System for comparison.

This supermassive black hole is the center of S5 0014+81, an extremely bright quasar known as a “blazar.” A quasar is a galactic center with a supermassive black hole surrounded by a huge amount of orbiting matter that is affected by the black hole’s gravitation so much that it emits light energy.

Located 12 billion light-years away from Earth in the constellation Cepheus, the black hole is 40 billion times as massive as the Sun and 10,000 times more massive than the Milky Way’s own black hole.

Since a black hole is a singularity, it doesn’t exactly have a definite size. Instead, the radius of its event horizon, also known as the “Schwarzschild radius,” is given as its measurement. For S5 0014+81’s black hole, it is 118.35 billion kilometers, that’s 40 times the radius of Pluto’s orbit.

Another measure of its massiveness is the brightness of the orbiting matter or the accretion disc, and this one is 300 trillion times as bright as the Sun. So, if it were to be at a distance of 280 light-years from Earth, then we’d receive as much energy from it as we do from the Sun.

But, S5 0014+81’s black hole is only the third most massive. The most massive black hole we’ve known so far is the one at the center of the quasar TON 618 located in the constellation Canes Venatici. It weighs 66 billion times as much as the Sun. (1, 2)

9 Massive abandoned hydroelectric tunnels 10 stories under Niagara Falls. 

The vicinity of Niagara Falls had been home to several hydroelectric power plants in both Canada and the US since 1882. The tunnels featured in the image above are part of the Toronto Power Generating Station in Canada that was completed in 1906. It was decommissioned in 1974 and is now a National Historic Site.

The plant’s generators sit on top of a very long vertical shaft below which are the turbines. When it was still functional, the power plant had a generating capacity of 137,500 horsepower (102,500 kW). (1, 2)

10 Cave of Crystals located 300 meters underground in Mexico.

Also known as the “Giant Crystal Cave,” the cave is located in the town of Naica in the Mexican state of Chihuahua. The cave is full of selenite crystals, a type of gypsum which crystalizes as transparent columns, and in this case, some of the largest ever found.

The crystals formed because the oxygen from the cool surface water mixed with the sulfide ions in the groundwater that was heated by an ancient magma chamber located three to five kilometers under the town. The process was a very slow one and took over 50,000 years to complete.

The largest crystal found in the cave to date is 12 meters (39 feet) in length, four meters (13 feet) in diameter, and weighs 55 tons. Because of the heat coming from below, the cave is extremely hot with air temperatures reaching up to 58 °C (136 °F) and humidity between 90 to 99%. So, the cave is relatively unexplored, as, without proper protection, it’s hard to stay there for more than 10 minutes. (source)

11 New Delhi’s Ghazipur landfill, nicknamed “Mt. Everest.”

After being opened in 1984 near the village of Ghazipur, the landfill functioned for years before reaching its full capacity in 2002. As of June 2019, the 13-million-metric-ton, mountainous heap of waste has risen as high as 65 meters (213 feet) and is expected to surpass the Taj Mahal’s height (73 meters, 239 feet) by 2020.

Now and then, the landfill experiences landslides and fires due to methane. After a particularly nasty landslide in 2017, there was a ban on dumping more waste there. But when the authorities could not find an alternative, the dumping continued after just a few days. (1, 2)

12 This large red sand dune in Namib desert.

Stretching over 2,000 kilometers across the western coast of South Africa, the Namib desert is known for its extremely tall sand dunes, many reaching over 200 meters. The dune featured in the picture above is called the “Big Daddy dune” located beside the Sossusvlei, a dry lake filled with salt and clay.

The dune is 325 meters high and faces another tall dune known as “Big Mamma.” Big Daddy, however, is only the second tallest sand dune, the first being Dune 7 which is 388 meters high and is located near the city Walvis Bay. (source)

Also see: 20 Pictures You Will Find Unsettling If You Have “Thalassophobia”