Got more time on your hands than money in your pocket or just want to explore the streets of Paris on foot, Paris a Pied is a good place to start.

Open to possibilities, go through their A to Z index starting with Ardoises (Slates.
Each option is illustrated by photos the most recent updates have a red title.

Under Eroticism, they offer a building at 276 boulevard Raspail with three medallions, the first of which (I quote) "illustrating the ages of man on the front of an upper-class residential building dating from 1905 (when the exposure of a woman’s ankle was very osé) shows a man naked to the waist locked in passionate embrace with a young woman with equally naked breasts. Happily, this appears to be all for a good cause, since the next medallion shows the couple with a child. Others are less explicit!"

If you liked the Fables of Jean de La Fontaine, I learned from Paris a Pied that "at least two buildings in Paris pay homage to the author of France’s best known fables, one at 40 avenue Félix Faure with the crow and the fox over the entrance, and the other at 10 rue d’Assas with medallions on the fourth floor showing the fox and the stork, the lion and the rat, the fox and the grapes, the oak and the reed, and another fable that the is ashamed to admit he is unable to identify."

Not ready to immerse yourself in all these details, Paris a Pied offers itineraries around a theme, for example Artists Studios in Montparnasse.

Another good pick for the Consumed to Thrifty

I discovered Paris a Pied thanks to Paris Greeter.

Related: Naughty, Romantic or Broke, Things to do in London, NYC or Toronto
and Running as City Tourism in New York