The religion Hinduism also called as Sanatana dharma is a major religion practiced predominately in Indian sub-continent and other neighboring countries in Asia, but once it was spread all across Asia and further, and It is considered to be the oldest surviving religion on the planet, with no single person as a founder.
These are the few rare and untold facts about Hinduism, which are unknown to the masses:

Dharma is above all:

The Hindu scriptures say that following dharma (the right way, righteousness, duties, and law) is more important than following the words of God himself, nothing in the universe can stop or harm a person if he’s fulfilling his dharma, including god himself, without which the universe and life will not exist.

There is no supreme god:

Though Hindu scriptures mention the supreme trinities Brahma (creation), Vishnu (energy), Shiva (emptiness, dark energy), but there were a lot of incidents mentioned in different Puranas, where the trinities take help of each other in making and sustaining of the universes, concluding there is more than one form of energies acting in creation and destruction of the universes.

God is formless:

10 avatars of lord vishnu
10 avatars of lord vishnu
Though many describe god to be in human form, according to the scriptures he has no form, shape, nor gender, he can take different shapes and forms that suit the situations. In the Dashavatara of Lord Vishnu, we can notice the different kinds of forms he takes to bring back dharma on earth.

There are no heaven and hell, but heavens and hells!

differeant lokas according to jain texts
differeant lokas according to jain texts
Unlike any other major religions that specifies earth, heaven and hell, but Hinduism scripts mentions 14 realms in the universe, 7 as hell and 7 as heaven, and every life forms in the universe will have a chance to take birth and death in all these realms based on their previous birth’s deeds/Karma. And earning Moksha/salvation is considered to be the greatest feat in the universe, which would free a person from a cycle of birth and death.

Unique calendar and time system:

The Hindu calendar or Vedic calendar, which is followed by all Hindus in India and across the globe, follows a circular concept of time, whereas the Gregorian calendar which is widely used across the world follows the linear concept of time. According to Vedic scriptures, everything is cyclical in the cosmos, so does the time.
In Vedic calendar and timing is based on movements of planets and other celestial bodies in space, and is very complex. The time is calculated so precisely to microseconds to the time dilation between the earth and other planets.

The fertility of earth decreases by each Yuga:

the size of kumbakarna, brother of ravana (Ramayana)
the size of kumbakarna, brother of ravana (Ramayana)
According to Vedic scriptures the years on earth is divided by 4 yugas, and by each Yuga passes the duration of time (years), fertility of life forms decreases by time:
  •          Sathya Yuga = number of solar years = 1,728,000 | average human height = 33f, 6 inches | average human life span = 100,000 years.
  •          Treta Yuga = Number of solar years = 1,296,000 | Average human height = 22ft 4 inches | Average human lifespan = 10,000 years.
  •          Dwapara Yuga = Number of solar years = 864,000 | Average human height = 11ft 2 inches | Average human life span = 1000 years.
  •          Kali Yuga = Number of solar years = 432,000 | Average human height = 5ft 3 inches | Average human life span = 100 years.

Ocean of knowledge:

Ancient Hindus passed on lot of scriptures and books, which are beyond science and imagination to the modern humans, which speaks about, administration, weapons, warfare, relation between planets and realms, advanced sciences that includes space travel, medicines, flying machine, description of different planets, evolution of cosmos and many more. Few of the important Hindu books are:
  •          4 = Vedas
  •          18 = Puranas
  •          108 = Upanishads
  •          Mahabharata
  •          Ramayana
  •        Bhagavad-Gita
  •          6 = shastras