na-adjective
mysterious; mystical
Describes something that feels beyond ordinary understanding, often with a spiritual, awe-inspiring, or uncanny quality.
この森には神秘的な雰囲気がある。
This forest has a mysterious atmosphere.
彼女の微笑みは神秘的だった。
Her smile was mystical.
謎 is a puzzle or riddle to be solved; 神秘的 describes an inherent, often unexplainable quality.
From 神秘 (しんぴ, 'mystery') + 的 (てき, '-like, -tic'). 神秘 is a Sino-Japanese compound of 神 (しん, 'god, spirit') and 秘 (ひ, 'secret').