We visited the Kintai Bridge in Iwakuni. It's not far off the Expressway, and very pretty. This bridge was modeled after the bridges in China at the time it was first built. According to the brochure, it is built in such a way that it actually gets stronger when weight is put on it.
There is a small fee to cross the bridge, but unfortunately, we were on a time crunch and couldn't stay. The original bridge was built in the 1600's, but washed away from a typhoon in 1950. The townspeople did all they could to save the bridge when the typhoon was happening. They couldn't stop it, so in 1953 they rebuilt it.