... interdimensional life and existence.
As a student of history, social culture and amateur understanding of astrophysics and quantum mechanics, a lifetime of learning and experience has given me an open mind to extrapolate possible theoretical concepts. One being the concept that higher states of existence and life has possibly visited our planet in the distant past.
Arthur C. Clarke's quote, "Any sufficiently advanced technology is indistinguishable from magic."
Wikipedia
As a young boy, I checked out library books on the Greek Myths and Legends all the time. I was fascinated with them, and they are the most known to me compared to the Egyption, Norse, Aztec-Mayan-Incan, and other ancient civilizations. I will concentrate on the Greek model.
Kardashev scale is a method of measuring a civilization's level of technological advancement based on the amount of energy it is capable of harnessing and using. The measure was proposed by Soviet astronomer Nikolai Kardashev in 1964 and was named after him.
A Type I civilization is able to access all the energy available on its planet and store it for consumption.
A Type II civilization can directly consume a star's energy, most likely through the use of a Dyson sphere.
A Type III civilization is able to capture all the energy emitted by its galaxy, and every object within it, such as every star, black hole, etc Wikipedia
From that established method, Type IV would consume several galaxies of energy, Type V would consume and entire universe of energy, Type VI would consume a multiverse of energy, and a Type VII would consume interdimensional use of energy in theory.
I believe that the Greek myths and legends stem from visits by beings of Type VI or Type VII. Ancient humans would witness the capabilities of such an advanced being as a supreme being. Immense power, strength, speed, knowledge, telepathy, telekinesis, pyrokinesis, flight etc... From these visits and interactions, the birth of the stories began around the campfires through oral tradition passing sown the centuries. With each retelling, more embellishment to harness the drama, romance and action to captivate the attending audience.
Where is the kernel of truth? Where does the embellishment start? That id in the eye of the believer or the skeptic.
Olympus, Atlantis, and the Underworld are real places but not on Earth. They are Greek names for the homes of the visiting beings. Sky, Sea, and Earth are represented as concepts that ancient man would understand. These places are located on a higher dimensional level. Access to them would require traveling through an interdimensional doorway. Human physiology isn't equipped to handle that journey.
The visiting beings had to make an assist for that. That's where the Ambrosia, the Nectar of the Gods, comes in. The ancient man would understand the concept of a potion or an elixir that you drink or eat as fruit. This is ingested to make changes in the body for transport to the realms of the visiting beings. Present day's understanding of science and medicine relates to DNA, RNA, amino acids, cell division with new programming and etc. The list is long.
This applied to the other civilizations as well. This is possibly how humans were moved to far corners of the Earth through advanced transportation methods by the visiting beings. This could account for similarities between the various civilizations where they couldn't have contact between all of them separated by the continents and the oceans.
Best part is they could still be visiting. Someone you know could be one in disguise. Some might have been involved with humans and had children. There could be inter-dimensional DNA in the human genome waiting to be realized.
Just a possibility that could fit the facts.