Černé jezero in the Bohemian Forest

Bohemian Forest

The Bohemian Forest, also known in Czech as Šumava , is a low mountain range in Central Europe. Geographically, the mountains extend from South Bohemia in the Czech Republic to Austria and Bavaria in Germany...

 is the largest and deepest natural lake

Lake

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

 in the Czech Republic

Czech Republic

The Czech Republic is a landlocked country in Central Europe. The country is bordered by Poland to the northeast, Slovakia to the east, Austria to the south, and Germany to the west and northwest....

 .

This triangular

Triangle

A triangle is one of the basic shapes of geometry: a polygon with three corners or vertices and three sides or edges which are line segments. A triangle with vertices A, B, and C is denoted ....

 lake surrounded with spruce

Spruce

A spruce is a tree of the genus Picea , a genus of about 35 species of coniferous evergreen trees in the Family Pinaceae, found in the northern temperate and boreal regions of the earth. Spruces are large trees, from tall when mature, and can be distinguished by their whorled branches and conical...

 forest is located about 6 km northwest of Železná Ruda

Železná Ruda

Železná Ruda is a town in the Pilsen Region of the Czech Republic. It is located in the Šumava Mountains, close to the border with Bavaria and the German town Bayerisch Eisenstein. It has been one of the important sports and touristic centres of the Šumava Mountains...

 under a 300-metre-high cliff on Jezerní hora (1,343 m) . It is of glacial origin

Glacial lake

A glacial lake is a lake with origins in a melted glacier. Near the end of the last glacial period, roughly 10,000 years ago, glaciers began to retreat. A retreating glacier often left behind large deposits of ice in hollows between drumlins or hills. As the ice age ended, these melted to create...

, a product of the Würm glaciation. The water in the lake is oligotroph

Oligotroph

An oligotroph is an organism that can live in an environment that offers very low levels of nutrients. They may be contrasted with copiotrophs, which prefer nutritionally rich environments...

ic. There is a natural outflow through Černý potok, a short stream which is a tributary

Tributary

A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...

 of the Úhlava River

Úhlava

The Úhlava is a long river in the Czech Republic, right tributary of the Radbuza. Its source is situated at the slope of Pancíř mountain in the Šumava mountains, Klatovy District at an elevation of . It passes villages and towns Nýrsko, Janovice, Bezděkov, Klatovy, Švihov, Lužany, and Přeštice...

. The main European water divide

Water divide

A drainage divide, water divide, divide or watershed is the line separating neighbouring drainage basins...

 runs across the mountain just above the lake. As a consequence, Černé jezero belongs to the water basin

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

 of the Elbe

Elbe

The Elbe is one of the major rivers of Central Europe. It rises in the Krkonoše Mountains of the northwestern Czech Republic before traversing much of Bohemia , then Germany and flowing into the North Sea at Cuxhaven, 110 km northwest of Hamburg...

, which finds the North Sea

North Sea

In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...

, while Čertovo jezero just 2 km away drains into the Danube

Danube

The Danube is a river in the Central Europe and the Europe's second longest river after the Volga. It is classified as an international waterway....

 and thence the Black Sea

Black Sea

The Black Sea is bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and the Aegean seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects that sea to the Aegean...

.

The oldest pumped-storage hydroelectric plant

Pumped-storage hydroelectricity

Pumped-storage hydroelectricity is a type of hydroelectric power generation used by some power plants for load balancing. The method stores energy in the form of water, pumped from a lower elevation reservoir to a higher elevation. Low-cost off-peak electric power is used to run the pumps...

 in the Czech Republic (built 1929-1930) is located here; the lake serves as its upper reservoir.

Role in Cold War Czech disinformation campaign

Due to proximity of the German

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 border (about 1 km), access to the lake was very limited during the Iron Curtain

Iron Curtain

The concept of the Iron Curtain symbolized the ideological fighting and physical boundary dividing Europe into two separate areas from the end of World War II in 1945 until the end of the Cold War in 1989...

 era. This was exploited by communist secret service

Secret service

A secret service describes a government agency, or the activities of a government agency, concerned with the gathering of intelligence data. The tasks and powers of a secret service can vary greatly from one country to another. For instance, a country may establish a secret service which has some...

s in Operation Neptune

Operation Neptune (Espionage)

In 1964, as part of Operation Neptune, the Czech intelligence apparatus publicly claimed to have discovered Nazi-era intelligence files hidden beneath the surface of Černé jezero lake. The claim was false. It was a Soviet deception operation....

 (1964) when the Czechoslovak StB

STB

STB is an acronym that can mean:* Sacrae Theologiae Baccalaureus – Bachelor of Sacred Theology* Set-top box – a television device that converts signals to viewable images* Simpson Thacher & Bartlett LLP -- a law firm...

 in collaboration with the Soviet KGB

KGB

The KGB was the commonly used acronym for the . It was the national security agency of the Soviet Union from 1954 until 1991, and was the premier internal security, intelligence, and secret police organization during that time.The State Security Agency of the Republic of Belarus currently uses the...

 covertly sank cases containing old captured Nazi SS RSHA

RSHA

The RSHA, or Reichssicherheitshauptamt was an organization subordinate to Heinrich Himmler in his dual capacities as Chef der Deutschen Polizei and Reichsführer-SS...

 documents in the lake and subsequently "accidentally discovered" them there. This came to light in The Deception Game, published in 1972 by Ladislav Bittmann.