1. The identity of the mysterious figure in the shadows remained unknown to the detectives.
2. The treasure map led the explorers to an unknown island in the middle of the ocean.
3. The doctor was baffled by the patient's illness, as it seemed to be caused by an unknown virus.
4. The artist drew inspiration from the unknown depths of her imagination.
5. The hiker stumbled upon an unknown trail that led to a breathtaking view of the mountains.
6. The explorer set out on a journey to discover the unknown regions of the Amazon rainforest.
7. The ancient civilization left behind many artifacts that shed light on their previously unknown customs and beliefs.
8. The astronaut gazed out at the vast expanse of space, filled with unknown planets and galaxies.
9. The author's latest novel delved into the realm of the unknown, exploring themes of mystery and suspense.
10. The young girl felt a sense of excitement as she embarked on a journey into the unknown, eager to see what adventures awaited her.