By faith, the walls of which city fell after the people marched around them for seven days?

Answer: Jericho

Hebrews 11:30 says the walls of Jericho fell by faith after the people had marched around them for seven days.

“By faith the walls of Jericho fell, after the people had marched around them for seven days.”— Hebrews 11:30 (BSB)