This is the 8174th most frequent Russian word.
луганскую
"Луганскую" is the accusative singular form of the adjective "Луганский," meaning "Luhansk" or "related to Luhansk," a region or city in Ukraine.
The word 'луганскую' is used as an adjective agreeing in the feminine singular accusative case with the noun 'природу' to describe something belonging to or related to Luhansk.
Луганскую природу часто описывают как очень живописную.
Luhansk's nature is often described as very picturesque.
Here, 'Луганскую' is an adjective describing 'область,' positioned in the feminine singular accusative case because it's the direct object of 'посетили'.
Они посетили Луганскую область во время своего путешествия.
They visited the Luhansk region during their journey.
In this sentence, 'Луганскую' should be corrected to 'Луганска' as a nominative noun to properly indicate the origin.