I was having a conversation with a friend the other day about our favourite metro lines (amongst waaayyy more interesting topics I might add). I went with 12 due to its lush racing green colour and ease of seat-getting each day on my way to work. She went with 4, that hot pink rollercoaster of a line where hanging on dearly to the nearest pole is extremely advisable (another friend told me that it’s such a stop-start thrill ride due to the fact they train the new metro drivers on it – sure explains a lot).

Before you start pointing at the sheer insanity of her choice (surely only line 13 is a more-hated beast), hear me out – there’s a pretty cool philosophical sentiment behind her choice. “It’s the only line that show you a complete cross-section of Paris”, she said, “from top to bottom”. A good thirty seconds later after I tried to work out how you could ‘see’ the very essence of Paris from a deep, dark underground tube, I realised that she was absolutely right. You’ve just got to pop your head out every few stops and you’ll see all the colours, textures, smells and sounds that the city has to offer.

Porte de Clignancourt, the northerly terminus of the line, starts you off with the flea market to end all flea markets, at the limit of the peripherique. Head downwards and within a couple of stops you’ll hit Marcadet-Poissonniers (literally fish-market, what the area used to be back in the day), where I’m told all the best people in the city live… From here you’re right on the edge of the popular part of the 18th arrondissement, but far enough removed from the tourist treacle to be comfortable.

Continue south and you’ll hit three of the ‘rougher round the edges’ stops (which in the opinion of some is being quite kind); Chateau Rouge, Barbès Rochechouart and Gare du Nord, where you’ll find yourself in one of the poorest parts within the city proper, known as Goutte d’Or. Now despite what Hemingway would have you believe, poverty doesn’t really equal romance, but here you’ll get to see the real multicultural foundations of Paris in their raucous, buzzing glory.

Stop by Strasbourg-Saint Denis to check out one of the old city gates (Porte Saint Denis) and then head to the commercial, pedestrinised centre at Châtelet-Les Halles where you can wander round the wonky buildings overlooking the brand new whatever-it-is-they’re-building above the underground shopping centre, and imagine what is was like when the area was home to a stinky old cemetery.

Cité is where the seeds of the city started growing, and is home to its iconic old lady Notre Dame. Head across (well, you’ll be under actually) the river and instant gentrification will be in the air as you head into the 6th and the Latin Quarter, taking in the la-di-da bits of Saint-Germain-des-Prés and Odéon (if you can find strolling space on the pavement), gazing in at the see-and-be-seens lazily grazing at the terraces of some of the city’s most famous cafés.

Montparnasse is dripping with artistic history almost as much as Montmartre, and you can scoot up the tower if you fancy trading your sewer rat’s-eye view for a bird’s-eye one. Denfert Rochereau is probably the last exciting-enough-to-surface-for metro stop what with the catacombs hiding in all their gothic glory below street level, though the markets at Raspail are a bio-lover’s dream (though as pricey as you’d expect). The line ends snaking through the residential comfort of the bottom of the 14th, bringing you to a atop at the new lower terminus, Marie de Montrouge.

So my friend was totally right. Follow the line and you’ll get to see every corner of Paris laid out for you (remember to stick your head above ground though, you’ll see naff-all if you stay on the train); the modern pockets, the way-back famous historical bits, and a complete cross-section of all of the social demographics the city has squeezed into itself. And if you spend a day metro surfing with a Navigo pass, you get to enjoy your Parisian visual cocktail for free. Oh yeah, and don’t forget to hang on (don’t say I didn’t warn you).