the.com/tunnel of love

means A slow-moving amusement park boat ride through a dark tunnel, decorated with hearts and soft lighting, designed to nudge couples into some necking.

from The phrase names a real carnival ride born in early 20th-century amusement parks (Coney Island's included), where boats drifted along a water channel through a darkened tunnel painted with romantic scenes — the darkness was the whole point, giving couples cover for a kiss. The name was soon lifted out of the midway and applied, half-mocking, to any rocky stretch of romance or marriage — the 'tunnel' being the dark, uncertain passage love runs you through.