Waterfalls form where a river flows over a steep precipice in its course.

Hussite wagon fort

The Hussites mastered the use of war wagons in the 15th century.


These special dolmens located in present-day Netherlands were built about 5,000 years ago.

Arab warrior (6th century)

The most important weapons of medieval Arab warriors were the bow and the sword.

Inca warrior (15th century)

The Incas´ rudimentary weapons were inadequate in their struggle against the Spanish...

Surface tension

Surface tension is the property of a liquid that allows it to obtain the smallest surface...

Auschwitz I Labour camp

The concentration camp established on Polish territory was the administrative centre of a...

Pula Arena (Pula, 1st century)

The Pula Arena, located in present-day Croatia, was one of the largest Roman...

Reaction of ammonia with hydrogen chloride

Ammonium chloride is the result of the reaction of ammonia and hydrogen chloride

Fuel cell

A fuel cell provides environment-friendly electric energy produced by the chemical...

Limbic system

The limbic system plays an important role in forming emotions and in learning.

Shale gas

This animation explains the technology of shale gas extraction.

AH-64 Apache (USA, 1975)

The Apache attack helicopter, named after an American Indian tribe, was developed for the...

Melting and freezing

During freezing hydrogen bonds are formed between water molecules resulting in a crystal...

Types of bridges

Types of bridges include beam-, arch-, suspension-, cantilever and truss bridges.

Air pollution

This animation demonstrates the main sources of air pollution: Agricultural, industrial...

Generating alternating current

Electric current can be generated by rotating an armature loop in a magnetic field.

El Niño

A periodic climate pattern that occurs across the tropical Pacific Ocean every five years.

Native American settlement (Crow Nation)

The Crow are Native Americans who inhabited the Yellowstone River valley.

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