Gifu Castle is located on Mt. Kinka, and it's known for being easy to defend and hard to attack. If you don't want to tire yourself out, you can just take the ropeway up.
Hasedera has a huge area dedicated to hydrangeas, with so many different varieties. Make sure to give yourself plenty of time to explore every corner and really take it all in.
Tsurugaoka Hachimangu is truly the symbol of Kamakura. The red buildings are really impressive. You can get there directly by the Enoden train, and Komachi Street nearby is also worth checking out.