from: Link

In the Bible                                                                                                                                             

The Nephilim were on the earth at that time (and also immediately afterward), when those divine beings were having sexual relations with those human women, who gave birth to children for them. These children became the heroes and legendary figures of ancient times. " Genesis 6:4

According to the bible in anti-Diluvian ages, giants populated the Earth; The bible also cites these beings in numerous verses. The most famous, surely, is that of Goliath that was defeated by David.

48 As the Philistine moved closer to attack him, David ran quickly toward the battle line to meet him. 49 Reaching into his bag and taking out a stone, he slung it and struck the Philistine on the forehead. The stone sank into his forehead, and he fell facedown on the ground.50 So David triumphed over the Philistine with a sling and a stone; without a sword in his hand he struck down the Philistine and killed him.51 David ran and stood over him. He took hold of the Philistine’s sword and drew it from the sheath. After he killed him, he cut off his head with the sword.When the Philistines saw that their hero was dead, they turned and ran. 52 Then the men of Israel and Judah surged forward with a shout and pursued the Philistines to the entrance of Gath[a] and to the gates of Ekron. Their dead were strewn along the Shaaraim road to Gath and Ekron.

In the Old Testament numerous giants are named, such as the Anakites, the Refei, Nephilim, who were present before the universal flood.

David Kill Golia of Pieter Paul Rubens

In the greek mythology                                                                                                                      

Beyond the bible, even in Greek mythology there are references to the giants, Titans were called, sons of Kronos and Rea.  The most famous tracks are found in Ulysses' epic, when he travels back to Ithaca, on the coasts of Eastern Sicily, meets Polifemo, the Cyclops, the men's devourer. Although archaeologists believe that what has led the legend of cyclops has been the find of elephant skulls, native to the island.

Annibale Carracci Galleria Palazzo Farnese, Roma.

In England                                                                                                                                                 

The Anglo-Saxon tradition is also rich in stories about giants, on the rise of hills, valleys and various other landscape forms created by the Giants themselves. In fact, they threw more than a dozen earthen blocks, and thrown huge rock blocks into the sea. In their poems, Anglo-Saxons often cite these huge beings that would exist before their arrival in England.

In Germany                                                                                                                                              

Even the Germans have their Giants, in the case of Tannchen, who would remove the rocks that made the Rhine waters stagnate between the black forest and the Vosges.