woman's world; feminine environment
Refers to a place or situation where only women are present, or where women dominate. Often used for all-female workplaces, schools, or social circles.
This workplace is a woman's world; I'm the only man here.
A girls' school is truly a feminine environment.
Compound of 女 (おんな, 'woman') + の (possessive particle) + 園 (その, 'garden'). Literally 'garden of women', used figuratively for a female-dominated space.