Just as the blue snail butler was pouring tea for Mom and Dad, a loud "Ding-ding!" echoed from the tiny entrance room far above their heads. Tilly looked up toward the ceiling of the cave. "That sounds like Leo's bicycle bell!" she exclaimed.

A moment later, a round turtle head wearing a bright red helmet peeked over the edge of the slide. It was Leo, Tilly's older brother. He was straddling a shiny silver bicycle and looking very confused at the gaping hole in the floorboards.

"Be careful, Leo!" shouted Dad, but it was too late. Leo leaned forward too far to see where his family was, and his front wheel dipped over the edge of the mossy slide. With a surprised yelp, he rolled right into the tunnel!

Instead of falling, Leo's tires gripped the soft, curved moss perfectly. He zoomed down the spiral ramp, picking up speed as he banked around the glowing turns. "Wheeeee!" he cheered, realizing this was the best bike path ever.

Leo shot out of the bottom of the slide and skidded to a halt near the crystal pool, splashing a little water on his wheels. Mom covered her eyes, but Leo was grinning from ear to ear. "Did you see that?" he asked breathlessly.

The blue snail butler clapped his hands slowly. "An impressive entrance, young sir," he said politely. Leo looked around at the vast underground space and realized the smooth stone paths were perfect for riding.

For the rest of the evening, Leo zoomed around the crystal pillars while Tilly chased him, laughing. The tiny house above was cramped, but down here, they had all the room in the world to play.