The phrase "lovely, dark, and deep," most famously from Robert Frost's poem "Stopping by Woods on a Snowy Evening," suggests a complex and layered feeling, encompassing:

• Attraction and Beauty: Lovely implies a sense of beauty, attraction, and aesthetic appeal. The speaker finds something inherently pleasing or captivating in the described subject, which in the poem's context is the woods.
• Mystery and Depth: Dark and deep suggest mystery, obscurity, and a sense of the unknown. The darkness can symbolize the hidden aspects of nature, the subconscious, or even the mysteries of life and death. The depth implies a vastness that is both alluring and potentially overwhelming.
• Intrigue and Allure: The combination of these elements creates a sense of intrigue. The speaker is drawn to the woods not just for their beauty, but also for the sense of mystery and the unknown that they represent. It suggests a place where one could lose oneself, either literally or metaphorically.
• Contemplation and Reflection: The phrase evokes a sense of introspection. The darkness and depth can represent the internal landscape of one's thoughts and feelings. The speaker may be tempted to pause and contemplate deeper meanings or personal issues.

In the context of Frost's poem, the woods symbolize a tempting escape or perhaps even the allure of death, contrasting with the obligations and responsibilities the speaker knows they must fulfill.