The seven lower worlds described in the Vedas are located in Naraka, the netherworld belonging to demons and souls that have become distanced from goodness and God.
Naraka is the plane of lower consciousness. Its regions are temporary hells of the mind and the universe. They are places where souls may wander for many ages or for just moments. Ancient scriptures accepted the relativity of time and space.
Thus, according to Vedic literature the duration of any soul’s existence in any world depends upon whether the time experienced by a particular soul expands or contracts and upon the time scales that are in play when souls migrate from world to world.
Hinduism believes that the destination of our soul depends upon our nature at the time of our death. Our nature is made up of different combinations of three attributes or qualities called gunas in Sanskrit.
These are sattva which is purity and truth, rajas which is desire driven activity, and tamas which is ignorance and inertia. Our actions and aspirations during our life create the sum of the attributes that make up our aura at death and determine what happens to our soul. Lord Krishna in the Bhagavad Gita describes the essence of the Hindu understanding of reincarnation in just a few short lines:
If when we die,
we are mostly Sattva,
our spirit gets born again in the world of the wise and the pure.
If we are mostly Rajas,
our spirit gets born again on earth.
If we are mostly Tamas,
our spirit gets born in the body of a dumb, ignorant being.
For more on Vedic Worlds, read On Hinduism by Irina Gajjar.