The Genitive/Possessive use
a) persons and related nouns (a man's job/ my life's aim etc.)
b) animals (the horse's mouth, the eagles' nest)
c) countries, cities, geographical areas (Russia's exports, China's battle against the Corona virus)
d) ships/vehicles (the train's heating system/ the ship's mast)
e) locations (St. Paul's Cathedral/ at my aunt's/at the butcher's/at Bill's = at his place)
f) time and distance (yesterday's news, a week's holiday, in three years' time, a ten minutes' break -> or a ten-minute break)
g) money and value (one millon's worth of diamonds/1,000,000.-'s worth of diamonds/ six euros' worth of ice-cream
h) expressions (a stone's throw, the water's edge, a winter's day or a winter day)
Often there's a choice: the car's engine or the engine of the car/ the town's population/the population of the town
Other cases: of-construction
The top of the hill/ banks of the river/legs of the chair/walls of the town/roof of the church
But you may say:
river banks, town walls, church roof (idiomatic/fixed expressions)