Wadakura Fountain Park is a lovely place to take a break. Enjoy a picnic, toss a Frisbee around or just lie on the soft grass and shut your eyes for a while.
If you're staying a while in Chiyoda, Wadakura Fountain Park is a great place to start your exploring. This recreation and green space is one of many attractions worth checking out here. Tokyo Skytree, Tokyo Tower, and Tokyo Imperial Palace are also ready to be explored nearby.