Final answer:
The phrase suggests the creation of a mental sanctuary within the mind, a space of personal spirituality and contemplation.
Step-by-step explanation:
Analyzing the phrase "...and build a fane / In some untrodden region of my mind," we can deduce that it does not imply the construction of a physical structure. Instead, it metaphorically refers to the creation of a mental or spiritual space within the mind, hence the most appropriate interpretation is that it suggests the creation of a mental sanctuary (B). The word 'fane' typically refers to a temple or a place of worship, symbolizing a sacred space. This sanctuary within the mind could be a refuge from the external world, a place of internal contemplation, or a mental construct where one can engage with one's beliefs or personal spirituality. This notion aligns with the concept of sacred architecture being not just a physical structure but also a mental or spiritual one, where the sacredness comes from the individual's beliefs and experiences within that space.