Dolmen Tomb: The earliest, the first ones

Burial Systems: The Act: Burial of the dead is the act of placing the corpse of a dead person in a tomb constructed for that purpose or in a grave dug into the earth.
Superstition: In cultures such as Mesopotamia, tombs and graves were cut into the ground in the expectation that the soul of the individual so buried would more easily reach the afterlife which was thought to exist underground.
Marking: Graves in the cultures of the ancient world were usually marked by a stone bearing the person’s likeness and name or by an elaborate tomb

Type: A Dolmen is a type of single-chamber megalithic tomb.
Dolmens were usually cove.

Elements: usually consisting of three or more upright stones supporting a large flat horizontal capstone (table).
Most date from the early Neolithic period (4000 B.C.E. to 3000 B.C.E.).

Construction: Dolmens were typically covered with earth or smaller stones to form a barrow.
Early in many instances, that covering has weathered away, leaving only the stone "skeleton" of the burial mound intact.

Oldest ones: The oldest known dolmens are in Western Europe, where they were set in place around 7000 years ago.
Artifacts: Human remains, sometimes accompanied by artifacts, have been found in or close to the dolmens. 

Dolmen sites
Korea: The largest concentration of dolmen in the world is found on the Korean peninsula.
With an estimated 35,000 dolmen, Korea alone accounts for nearly 40% of the world’s total.
India: There are also dolmens in Andhra Pradesh, Karnataka, Kerala and Tamil Nadu in South India.
Africa: ancient site, which contains a necropolis with dolmens.

Types of Burial Places:
Great dolmen
Passage grave
Polygonal dolmen
Rectangular, enlarged or extended dolmen
Simple dolmen