When I was traveling Nanking, I usually take a bike.
I wasn't a cyclist before that journey.
There are many shared bicycles in Nanking.
In Nanking, I saw bicycle graveyards.
Countless abandoned bicycles were piled up there.
Bicycles were introduced in the 19th century and now number about one billion worldwide.
Cycling is regarded as a very effective and efficient mode of transportation optimal for short distance.