Aztec religion permeated every area of life. The world was divided into four quadrants centered around the capital of Tenochtitlan. There were 13 heavens in concentric layers above the world, and 9 underworlds in concentric layers below. They have been described as wheels within wheels. Heaven and earth intersected in the temple in Tenochtitlan.
Where many beliefs hold that the nature of the afterlife is based on how they lived their lives, Aztecs believed that how a person died determined the nature of their afterlife. The more honourable and premature or unusual a death was, the more esteem they were given, reflected in their going to a paradise in heaven. The dead were buried with items to help them in their afterlife journey.
Death of a warrior in war resulted in an afterlife in paradise in the east where he was part of the morning sun's rising (the god Nanauatl). Death of a warrior in sacrifice to the war god (Huitzilopochtli) would mean joining the god in the battle against darkness. If a woman died in childbirth, she would go to paradise in the west and was part of the evening sun's setting. Those who died by remarkable deaths - by lightning strike, unusual diseases, violence or drowning for instance - went to the paradise Tlalocan located within the 13 heavens. Some may eventually reincarnate as animals or insects or ultimately humans.
Most will at some point go through Mictlan - the underworld, ruled by King Mictlantecuhtli ("Lord of the Underworld") and his wife. This was the outcome for those who died unremarkable deaths - from old age or common illnesses - they went to the Aztec underworld where they would undergo harsh trials to journey through the nine levels.
Only those who died in childbirth or had been sacrificed went to Heaven, so death from other causes was dreaded among most Mayans. Mayan afterlife was a dangerous journey of the soul through the underworld, a cold and unhappy place represented by the jaguar (symbol of night) and full of malevolent gods.
Most Mayans' souls, even the rulers' souls, went to the underworld. Kings however were thought to have supernatural powers and were reborn as gods in the Sky World.