The globus cruciger, also known as "the orb and cross", is an orb surmounted by a cross. It has been a Christian symbol of authority since the Middle Ages, used on coins, in iconography, and with a sceptre as royal regalia.
The cross represents Christ's dominion over the orb of the world, literally held in the hand of an earthly ruler. In the iconography of Western art, when Christ himself holds the globe, he is called Salvator Mundi (Latin for 'Saviour of the World'). For instance, the 16th-century Infant Jesus of Prague statue holds a globus cruciger in this manner.
Holding the world in one's hand, or, more ominously, under one's foot, has been a symbol since antiquity. To citizens of the Roman Empire, the plain spherical globe held by the god Jupiter represented the world or the universe, as the dominion held by the Emperor. A 2nd-century coin from the reign of Emperor Hadrian shows the Roman goddess Salus with her foot upon a globus, and a 4th-century coin from the reign of Emperor Constantine I shows him with a globus in hand. The orbis terrarum was central to the iconography of the Tetrarchy, in which it represented the Tetrarchs' restoration of security to the Roman world. Constantine I claimed to have had a vision of symbol of Christ above the sun, with the words "In this sign, you shall conquer" (Latin: "In hoc signo vinces"), before the Battle of Milvian Bridge in AD 312. This symbol is usually assumed to be the "Chi-Rho (X-P)" symbol, but some think it was a cross. Consequently, his soldiers painted this symbol on their shields and then defeated their foe, Maxentius.With the growth of Christianity in the 5th century, the orb (in Latin works orbis terrarum, the 'world of the lands', whence "orb" derives) was surmounted with a cross, hence globus cruciger, symbolizing the Christian God's dominion of the world. The Emperor held the world in his hand to show that he ruled it on behalf of God. To non-Christians already familiar with the pagan globe, the surmounting of a cross indicated the victory of Christianity over the world.