h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

It's dull and grey, it's mobbed with people, motorists drive like complete maniacs, and the Eiffel tower is huge let down!

You only get let down the tower after you've been up...
Best not to go up on foggy days, otherwise - great view. A tad expensive, but so was bloody madam twoswords in london.

As for the motorists, they're only as bad as most cities to each other, but they give way to 2 wheels, which suits me just fine...

Well, I went to Edimburg and Glasgow. Those are dull and grey, my friend....

Dull? Let down!?
Paris is an adventure in itself! Simply being in it is the best way to spend a spare day... or week.
Not only can you play thrilling games such as "crossing the road" and "getting on the wrong RER line", you can take a break by the river with a handful of pastries bought at the local patisserie. You can be cultural on the Montmartre, or get your charicature done. You can be less cultural at the base of the Montmartre... another story. You can shop for anything anywhere you like (if that's what boils your soup). You can be a tourist outside any number of huge religious buildings or museums. If your French is good enough and you've stuck to the rules laid out in the main article about not looking like a tourist, you can even convince a few cross-Atlantic tourists that you are a local (this researcher has done just that).
And whether viewed at night or by day, from the ground or atop that famous girder construction, it's anything but grey!