A huge sign reads "Nullarbor National Park, Thirty-three Miles" in English on the side of the road ahead, and underneath the line, a prominent left-turn mark marks the route to Nullarbor National Park.

Tang Feng and Sophia glanced at each other, and then nodded in agreement, Tang Feng hit the steering wheel, and the car immediately turned a corner, left the El Highway, and drove onto a sandy road that was not very wide, heading towards the depths of the vast Nullarb Great Plains.

In the vast Australia, there are many national reserves, all kinds, strange, this is mainly because of the huge continent of Australia, there are too many types of organisms, and many of them are unique to the Australian continent, coupled with the unique landform of the Australian continent, this will form many national reserves.

According to statistics, in Australia, a country with an area of more than 7.6 million square kilometers and a population of just over 23 million, there are as many as 618 national protected areas and parks alone, which is a terrifying number.

In fact, Australia has long been known for its man-made parks and its natural reserves. As early as 1836, Tasmania was declared a Natural Scenic Area. In 1866, an area of more than 20,000 square kilometres around the Jenolen Cave in New South Wales was also declared a scenic reserve. As early as six years before the announcement of the establishment of the world-famous Yellowstone National Park Scenic Reserve in the United States, that is, in 1879, the world's first man-made national park - Sydney South Park was announced, this park was renamed Royal National Park after 1954, and in 1982 it was announced that the establishment of Curingmustard Chase National Park in the north of Sydney.

By 1916, all six states of Australia had their own national protected areas, and now, the protected area on the Australian continent is 58 million hectares, accounting for about 7.55% of the total area of the Australian continent. In addition, there are more than 2,700 designated protected areas scattered across the country, as well as 145 marine protected areas covering almost 38 million hectares.

These national, protected and marine protected areas can be found throughout Australia in a wide range of ways, from national protected areas such as the First Botanical City and Aboriginal Areas, to huge national marine parks such as the Great Barrier Reef, and geoparks such as Nullarbor National Park, where Tang and Sophia are going today, known for their sinkholes and strange landscapes.

Although the road is not wide, it is very straight, all the way, there is basically no turning place, and there are very few vehicles here, Tang Feng drove for more than thirty miles, and he didn't even encounter a single car.

Soon, a huge crater appeared on the ground in front of him, because it was not clear from a distance, but it was undoubtedly an existence similar to a sinkhole.

In fact, the term Tiankeng was first proposed by Chinese geologists in 2001, and it was not until 2005 that the academic term "Tiankeng" was internationally recognized. However, in foreign countries, especially in Australia, this kind of large karst negative terrain is generally habitually called "cave".

The sinkhole that Tang Feng and the others encountered was not very large, the diameter was about more than thirty meters, and in the strict sense, this huge natural pit was not a sinkhole in the real sense at all.

The so-called sinkhole has some limited standards in the academic world, and the depth and width are more than 500 meters for the super sinkhole, and there are only three cases in the world, all in China (the Xiaozhai sinkhole in the mountain city and the Leye Dashiwei sinkhole in the land of Bagui all belong to the super sinkhole); Large sinkholes with a depth and width of between 300 and 500 meters are large, with 16 cases worldwide and 9 cases in China; A sinkhole with a depth and width between 100 and 300 meters is a standard sinkhole.

A sinkhole below the standard of a sinkhole cannot be considered a real sinkhole, but now basically no one cares about that, as long as the sinkhole is mysterious enough, then it will attract a large number of tourists to come and watch.

In Australia, most of the sinkholes belong to the substandard "sinkholes", no wonder the Australian people have always insisted on calling these sinkholes "caves". However, although these small sinkholes in Australia cannot be a real standard sinkhole in terms of width, in terms of depth, there are few sinkholes in the world that can compare with these magical "caves" in Australia.

As mentioned earlier, the Cokerbidi water cave located in the depths of the Naraber Plain is actually a sinkhole, but the width of the sinkhole is not very large, but the depth can only be described as "unfathomable", and the French divers have dived to a depth of 4,500 meters with the help of submersibles, but still have not reached the bottom of the water hole.

Of course, there are not many sinkholes as deep as the Coker Biddy Water Cave, even in Australia, but there are many sinkholes here, although they are not very big, but the scenery inside is very beautiful, and because the depth is not enough, most of these caves are inhabited by some animals, and they are all unique to Australia.

It is for these reasons that these sinkholes in Nullarbor National Park attract the attention of many tourists. For example, in this inconspicuous sinkhole in front of you, there are forty or fifty people gathered around it.

On the way here, Tang Feng didn't meet anyone, but when he arrived at the destination, there were so many tourists suddenly, which was really strange.

But looking at the ruts around this sinkhole, Tang Feng realized that driving on the Nulraber Plains does not necessarily have to follow the road, the flat Nullarbor Plains are everywhere, you can walk casually!

This sinkhole is not too deep, looking down at it is about more than ten meters, and the sinkhole is not straight up and down, there is a gentle slope formed by the collapse of the ground surface on the east side of the sinkhole, whether it is a tourist or an animal, you can go up and down this gentle slope.

When Tang Feng and the others arrived here, they found that there were not only forty or fifty people on the top of the sinkhole, but also twenty or thirty people at the bottom of the sinkhole.

This sinkhole is actually a bit like an inverted funnel, small at the top and big at the bottom, if it weren't for the existence of that collapsed gentle slope, if you want to go down such a sinkhole, I'm afraid there is really no good way to go up and down except by abseiling.

However, it is precisely because of this shape that the bottom of the sinkhole appears to be very spacious, twenty or thirty people gather below, it does not appear congested at all, on the contrary, some of the aboriginal animals in the sinkhole, do not seem to be so panicked in the face of these visitors, the grass should eat grass, the bend of the walk, anyway, as long as those visitors do not deliberately approach those animals, those animals generally will not escape.

Obviously, the aboriginal animals here are already familiar with the daily visitors, and perhaps after the initial panic, these intelligent animals have also discovered that these tourists are not terrible, so they live in peace with the tourists in this way. The most famous of these aboriginal animals is naturally the spokesperson of Australia, the kangaroo.