This is the 1493rd most frequent German word.
unbekannte
"Unbekannte" means "unknown" or "stranger" in English.
In this sentence, 'unbekannte' is used as an adjective describing the noun 'Land', meaning 'unknown' or 'not familiar'.
Das unbekannte Land birgt viele Geheimnisse.
The unknown country holds many mysteries.
Here, 'unbekannte' is used as an adjective to modify 'Stimme', indicating that the voice is unfamiliar or not recognized.
Eine unbekannte Stimme erklang in der Dunkelheit.
An unknown voice resounded in the darkness.
In this instance, 'unbekannten' is an adjective describing 'Herausforderung', suggesting a challenge that has not been encountered before.