The so-called Dantian is located on the golden section of the human body.
The upper Dantian is the position where the length of the head is multiplied by 0.618 starting from the chin (for most people, it is between the eyebrows).
The middle Dantian is the position where the length of the torso is multiplied by 0.618 from the lower yin (for most people, it is the middle of the two nipples).
The lower Dantian, calculated from the feet, is the position where the length of the height is multiplied by 0.618 (for most people, it is near the belly button).
As long as you study carefully, you will also find that several other major acupuncture points in the human body are related to the golden section.