Museum of the Middle Ages. Lots of medieval arts and crafts -- paintings, tapestries, sculptures, religious objects such as reliquaries or incense holders; jewelry, housewares. I remember a tapestry that portrayed a robbery (at least as far as an eye untrained in art and medieval history could guess) -- you have to wonder if back in the day this was a substitute of crime scene photography. Did the maker of the tapestry present it as evidence in court? :-)
Some tapestries from the Middle Ages were hyper-realistic. Look at the monkey (?) at the bottom of this hunting scene -- is it really doing what I think it's doing? And why was it so important to put that in the picture? :-)
Outside of the Museum of the Middle Ages there is a huge pit with uncovered ruins of Roman baths. The whole area is fenced off, and I'm not sure if it is ever open; if there was a door inside of the museum to get to the excavated area, we couldn't find it.
Cluny museum. Paintings, lots of paintings -- mostly impressionists and expressionists. Or maybe it was just one special exhibit we visited. Could not spend much time in the museum, as we arrived 1 hour before closing. Turns out that was cutting it very close: we were among the last few people to were admitted. So, there was plenty of Van Gogh and Gauguin, and... well, that's where my familiarity with painters of that era ends, so I can't list other undoubtedly famous names.
Pere Lachaise cemetery, where many famous people are burried (including Jim Morison). It's a quiet little city-in-the-city with its own streets and alleys. Famous or not, some tombs seem to be abandoned, judging by how trashed they are. It's spooky to be there near closing time: a sign says the cemetery closes at 6, but there are no guard around to usher the stragglers out. Will they lock the gate leaving the slowpokes inside until morning? That's what you wonder as you rush this way and that trying to find the exit, or look for any signs of other people heading towards exits. (Spoiler: we got out! The exit wasn't really locked. No luck in getting to spend a night stretched on Jim Morrison's grave. :-))
More pictures from my trip are in my photo gallery.