Genuine awe is experienced all too rarely. It's what we feel when we become aware of a numinous presence (a term coined by Rudolf Otto, who died the year I was born). It's an intensely spiritual feeling.
C.S.Lewis, in his autobiography, Surprised by Joy, gave it a different connotation, but he was talking about the same thing. (A book worth reading, but seekers will need to filter out the religious content if they want to find the spiritual essence.)
For me the last time I experienced that level of awe was about 1970. It's an experience I'll never forget. I wrote a poem about it a few years later, but I won't quote that here. It's personal.
But since then I've experienced shadows of awe (nobody who has experienced the real thing would confuse the shadows with the reality) while watching the night sky, or sitting on a cliff contemplating the ocean, or walking through the mountains.
But you asked about the last time. That would probably be in the late 1990s in the Australian Alps.