This is the 4070th most frequent Russian word.
нижегородские
"Нижегородские" means "related to Nizhny Novgorod or its people."
This sentence uses 'нижегородские' as an adjective to describe the streets belonging to Nizhny Novgorod, implying the city's name used as a descriptor.
Нижегородские улицы красивы осенью.
Nizhny Novgorod streets are beautiful in autumn.
Here, 'нижегородские' is used as an adjective qualifying a group of artists associated with Nizhny Novgorod.
Нижегородские художники представили свои работы на выставке.
Nizhny Novgorod artists presented their works at the exhibition.
In this case, 'нижегородские' modifies 'края' ('region') to specify the location related to Nizhny Novgorod, indicating properties or association with the city.