Old Lyon is the largest Renaissance district in Lyon. Along with its many other artistic and architectural treasures, are the traboules (corridors, top) and the courtyards (bottom). They date from the 4th century, and the French used them to to escape from the enemy during the French Revolution and WWII.
They were originally used to transport silk from the factories to the silk merchants without the merchandise getting damaged from inclement weather. The villagers used these passageways to get water from the river.
Finally, Lyon is an UNESCO World Heritage Site. There is much more to see and do here that the one day we had was not enough. I especially think it would be cool to be here during the Festival of Lights from December 6 to 9, every year. It started as a thanks to Saint Mary for saving the city from the plague in the 17th century. Every year the buildings are lit up. Mere words cannot seem to describe it: http://www.fetedeslumieres.lyon.fr/en.