I found Honmoku Citizens Park quite by chance. We were driving to Sankeien Garden in Yokohama to see early autumn leaves there, and suddenly realized that it was a national holiday, and so Sankeien Garden could be unbearably crowded. In the worst case scenario we wouldn't be able to park the car and would have to head back home!
So I hastily checked the map to find an alternate destination, and I found this park located just next to Sankeien Garden. When we arrived, we found a considerable parking space where we could park our car for 200 yen per hour, and a not-at-all-crowded park despite the holiday. This park was built for local citizens when the Honmoku Pier and the surrounding area were reclaimed. The park is spacious with tennis courts, a big lawn, a playground and more. Quite a nice place to have a weekly picnic or walk a dog. When you wake up from a luxurious nap on the big lawn you can easily head to Sankeien Garden next door to feel history!