Hauntingly is the adverb for that same sad-and-beautiful, hard-to-forget feeling. People most often put it before an adjective: hauntingly beautiful, hauntingly sad, hauntingly familiar (you feel you have met this before, and it stays with you). It tells you how something looks, sounds, or feels. It is not how someone “haunts” a house. Same warning as haunting: this entry is not the ghost word, though the family is the same. You will meet it in writing about music, film, and places more than in everyday talk.