Par monts et par vaux

Annette a couru par monts et par vaux pour trouver une boulangerie ouverte un lundi à 13h. Spoiler : elle a fini au supermarché.
The French expression « par monts et par vaux » means “over hills and through valleys,” and more broadly, “all over the place” or “far and wide.” It suggests moving across all kinds of terrain - both literally and metaphorically - and is often used to evoke the image of tireless wandering, travel, or exploration, whether for pleasure, necessity, or effort.  The expression doesn't carry, however, the sense of chaos or or being dragged all over the place that the English cousin "Over hell and breakfast" does. The latter is also more colloquial and rough in tone.

Monts means mountains or hills.  Vaux is the plural of val - an old or literary word for valley.  So the phrase literally means “through mountains and valleys." 

Origin

The phrase dates back to the Middle Ages, where poetic and chivalric literature often used expressions of nature and geography to describe heroic quests and long journeys. It was a time when travel meant trudging across all kinds of landscapes - hills, valleys, rough paths - in search of markets, work, or news. Over the centuries, it shifted from a literal description of arduous journeys to a figurative way of saying “everywhere” or “far and wide.” Today, it’s often used in storytelling or formal speech, adding a slightly old-fashioned, almost literary charm to the idea of being constantly on the move.  The pairing of opposites (mountains and valleys) also fits a common rhetorical device in French (and Latin) literature known as merism: where two extremes are used to refer to a whole.

The word “vaux”, now archaic, survives almost exclusively in fixed expressions like this one, or in toponyms (like Vaux-le-Vicomte).

Examples

Depuis qu’ils ont pris leur retraite, ils courent par monts et par vaux pour voir leurs petits-enfants.
Since they retired, They've been dashing all over the place to visit their grandchildren.

Les journalistes ont couru par monts et par vaux pour couvrir l’événement.
The journalists raced far and wide to cover the event.