To give spiritual meaning to our lives, we often turn to a deity. There is something deep about it that makes us feel helplessly small and somehow gives us comfort. Personally, I can't think of anything bigger, deeper and for lack of another word, more hypnotic than the universe itself.
If we disregard deities, the very existence of the human being takes a deeper spiritual meaning, as the part of the universe that has evolved to be able to try to understand itself.