the other side of a river; across the river
Refers to the area on the opposite bank of a river. Often used in a literal geographical sense.
You can see a small shrine on the other side of the river.
I cross the bridge to the settlement across the river.
the other side of the tracks; poorer area across the river
Figurative use implying a socially or economically disadvantaged neighborhood, often separated by a river. This sense is sensitive.
He grew up in a poor neighborhood on the other side of the river.
Schools on the other side of the tracks rarely get enough funding.
From 川 “river” and 向こう “the opposite side,” literally “the other side of the river.”