There are several synonyms for the phrase "parts unknown." Some alternatives include "uncharted territory," "terra incognita," "out-of-the-way places," and "remote corners of the world." These phrases are often used to describe areas that are unfamiliar, inaccessible, or difficult to navigate. "Parts unknown" may also refer to locations that are mysterious or unknown in terms of their history, culture, or significance. Other synonyms for this phrase include "mystical lands," "beyond the horizon," and "terra firma." Each of these synonyms captures the sense of adventure and exploration that comes with discovering new and exciting places.