I went on a nighttime bike tour a few years back in Paris that was tons of fun. I'm not sure how safe I'd feel navigating on my own, but by tour I felt totally comfortable. The last time we were in Paris, we noticed one Saturday or Sunday that they closed part of the road that are directly along the Seine (at River leve) to cars and allowed only bike/pedestrian traffic. I wish we'd rented bikes that day. That would have been fun.
One thing I'd say about the rentals. I'm not sure about their various payment options. I know you can tickets for the bikes online. At the terminals themselves, if you can only pay by credit card, that may limit you. All/most of Europe use a different type of credit card than we do in the United States. European cards have embedded chips in them that require the use of a PIN, while American cards use a magnetic strip. American cards generally work fine at shops/restaurants, but at automatic terminals (like those at a train or metro stations), not so much. I learned that the hard way a few years back. So, look into how to pay for the bikes if you think you'd like to try it.
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher