I like Early to High Middle Ages, basically from the fall of the Western Rome to the Mongol invasion. Like the other anon said, it just feels unique, genuine and different, almost cryptic and hidden due to how the Modernity, Enlightenment and Renaissance relied on creating a completely false imaginary askew retarded version of it simply to feel better about themselves.
I also like Pleistocene, because it is a primordial cradle of every human civilisation. It stretches from the Palaeolithic, before the first ethnic cultures in the modern sense even existed, to the Bronze Age Collapse, which is another part of human history that feels almost alien, borderline forgotten as if it either never happened, or was just made up in some fantasy fiction, while in reality there existed amazing deeply complicated and well-developed cultures with cities and thousands upon thousands of people, living their every day lives.