| Clue | Source | Date |
|---|---|---|
| Innermost parts | Premier Sunday | 25 Feb 2024 |
| Least accessible areas | The Washington Post | 29 Apr 2017 |
| Least accessible areas | LA Times Daily | 29 Apr 2017 |
| Least accessible areas | ||
| Least accessible parts | ||
| Least accessible parts | ||
| Hard-to-reach places | ||
| Hard-to-reach places | ||
| Oft-unexplored areas | ||
| Oft-unexplored areas | ||
| Parts hardest to reach |