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The world’s largest lake occupies about 371,000 square kilometers, stretches nearly 1,200 kilometers, borders five countries, and reaches over 1 kilometer in depth.
The water continues until it disappears into the horizon. In some spots, those standing on the shore cannot see the other side and might imagine they are facing an ocean. However, this massive body of water is contained between lands, with no natural connection to the major oceans. According to Guinness World Records, the Caspian Sea occupies about 371,000 square kilometers and is recognized as the largest lake on the planet by area.
The size helps explain why it is called a sea. NASA notes that ancient peoples viewed this quantity of water as if they were facing an ocean. Today, five countries share its shores, major cities have grown alongside it, and ships traverse distances that can exceed one thousand kilometers within a lake completely isolated from the ocean.
The lake stretches for nearly 1,200 kilometers
The Caspian Sea measures approximately 1,199 kilometers from north to south, according to Guinness. Its width varies significantly along its length, ranging from about 196 kilometers to approximately 435 kilometers.
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This means that a person could travel over one thousand kilometers following the lake without reaching its end. Its coastline stretches for about 7,000 kilometers, a distance greater than many international trips made by road.
The scale becomes even clearer when viewed from space. Photos taken by astronauts show a mass of water so large that it occupies a significant portion of the image even when observed from hundreds of kilometers above the Earth.
Five countries share the shores of the same lake
To the north and northeast lies Kazakhstan. Russia appears to the northwest, Azerbaijan occupies part of the western shore, Iran is to the south, and Turkmenistan runs along a significant portion of the southeast side.
Consequently, no single nation controls the entire shoreline. Ports, cities, industrial areas, fishing zones, and large oil and gas fields are spread across different sides of the same lake.
This positioning also places the Caspian Sea in a zone between Europe and Asia. Its waters separate desert regions, vast plains, mountainous areas, and cities that rely directly on the lake for transportation and economic activity.
It looks like a sea, has salty water, but remains a lake
The question arises due to its name. If it is called the Caspian Sea, why does it enter the records as the largest lake in the world?
The answer lies in the fact that it is a vast body of enclosed water within the continent. There is no natural outlet that leads its waters directly to an ocean. Scientific studies describe it as the largest closed body of water on the planet.
The water is also not entirely fresh. The salinity varies from one region to another. In the north, where major rivers discharge freshwater, it is much less salty than in the deeper southern parts.
More than 100 rivers feed into it
The Caspian receives water from around 130 rivers. The most important ones flow in from the north, where the shallowest part of the lake is located.
The Volga River is the main player. Together with the Ural River, it accounts for more than 80% of the water brought to the Caspian Sea by rivers, according to a study published in Communications Earth & Environment.
The problem is that this water comes in but does not find a river that can carry the excess to another sea. Much of it is lost to evaporation as water transitions to the air. Therefore, changes in temperature, rainfall, and river flow can significantly alter the size of the lake.
The north is shallow while the south exceeds 1 km in depth
The same lake holds two nearly opposite scenarios. In the northern part, the average depth is only about 5 meters, with large stretches being even shallower.
As you move south, the bottom drops off. The central area reaches 788 meters, while the southern region exceeds 1,000 meters in depth. Scientific sources place the maximum point at approximately 1,025 meters.
Thus, the same body of water features shallow regions where ice can appear in winter and others where multiple large buildings could be stacked atop each other before reaching the surface.
Its surface lies below sea level
There’s another measurement that may seem strange. The Caspian Sea’s surface is not at the same level as the Atlantic or other major oceans.
It stands approximately 27.5 meters below the global average sea level, according to a scientific study published in 2025. NASA had recorded values close to 27 meters below sea level in previous surveys.
This occurs because the Caspian occupies a large depression within the continent. Despite its enormous size, it remains trapped in this basin and cannot simply drain into the oceans.
Its volume reaches about 78,000 km³ of water
The size is not apparent only when measuring the surface. The Guinness World Records estimates a volume of approximately 78,200 cubic kilometers of water within the Caspian.
One cubic kilometer is equivalent to one trillion liters. This figure helps illustrate why this place behaves very differently from a common lake found in a city or park.
Even with so much water, however, its level can rise and fall considerably. As there is no natural connection to the ocean, the balance primarily depends on what enters through rivers, rain, and what disappears through evaporation.
The lake also houses animals that exist nowhere else
This isolation has fostered a unique fauna. One of the most well-known examples is the Caspian seal, a species found only in this region.
The lake also hosts different sturgeon species, fish historically linked to caviar production. NASA has emphasized for decades the importance of these animals and fishing for nearby communities.
A study from 2025 also points out more than 300 species of invertebrate animals found only in this region and 76 species of fish that do not exist naturally anywhere else.
Oil and Cities Grew Alongside the Water
The Caspian Sea also occupies a region rich in oil and gas, with exploration facilities appearing at different points along its shores and even in areas far from the coast.
NASA highlights the Absheron Peninsula in Azerbaijan as one of the historical centers of oil production in the region, with the capital, Baku, developing right next to these waters.
Ports also rely on the lake’s water level to operate. When the water recedes, channels can become shallow, vessels face difficulties, and structures built near the former shore can become increasingly distant from the water.
The Coastline Can Shift by Dozens of Kilometers
The largest lake on the planet does not have a fixed shoreline. A study published in April 2025 analyzed satellite images and found an impressive change in the northeastern Caspian Sea.
Since 2001, in some areas, the waterline has receded by more than 56 kilometers. Regions that were once covered have turned dry, especially in the northern areas, where the lake is quite shallow.
This change does not require the water level to drop by several meters to produce a significant horizontal effect. When the bottom is nearly flat, even a small drop can cause the waterline to recede by many kilometers.
The Largest Lake in the World is Shrinking
Researchers indicate that the level of the Caspian Sea has been declining in recent decades. Between 2006 and 2021, the decrease reached approximately 1.4 meters.
Rising temperatures contribute to increased evaporation. At the same time, changes in rainfall and the amount of water arriving from rivers alter the balance that keeps the lake full.
Scientific models indicate further declines during this century. Depending on the level of global warming, studies suggest reductions of several meters by 2100, with more extreme scenarios approaching 21 meters.
A Drop of 5 Meters Would Already Change the Map
Five meters may seem insignificant in a region that exceeds 1,000 meters in depth. However, in the north, much of the Caspian has only a few meters of water.
The 2025 study calculated that a drop of 5 meters could transform approximately 77,000 km² of water into land, nearly 20% of the current surface area used in the model.
Ports, breeding sites for animals, and other important areas could become distanced from the new shoreline. The study also warns of billions of dollars in industrial and civil structures that may lose their functionality as the water recedes.
The Giant of 371,000 km² May Shrink Within a Generation
Today, Guinness recognizes around 371,000 km² for the world record. Other studies arrive at slightly different figures because the area changes along with the water level and also depends on the method used for measurement.
Nonetheless, the record remains. No other current lake has a surface area close to that of the Caspian. It stretches nearly 1,200 km, borders five countries, and at its deepest point, exceeds one kilometer to the bottom.
For thousands of years, its size led people to call that place a sea. Now, satellites can track something that those living on its shores are already beginning to see on the ground: in shallow areas, water is receding and leaving new strips of land behind.
The largest lake on the planet remains large enough to feel like an ocean. The difference is that, unlike oceans that rise with global warming, this giant enclosed between Europe and Asia may face the opposite problem.
