the cedars were planted; That really impressed m

Yes, it is said that the cedars were planted in 1618, the beginning of the Edo period.

Many samurai would walk there to go to Kyoto and so on. That really impressed me.

Singular

流(flow)

図(figure)

I can't imagine it!

Japan is about the size of California, to give you a sense of scale if you look at a map.
That’s huge! I can’t imagine it! I’d like to go to America one day.