Might be cool for the backyard….GENIUS…Line a pathway with rocks painted in glow in the dark paint. During the day they “charge” in the sun and in the evening they reflect the stored light. Rust-Oleum Glow in the Dark Brush-on Paint.
You can also buy glow-in-dark stones and pebbles that are already infused with the glow. They soak up the light during the day, and glow at night. Like solar-powered stones.