An easy day trip from Kyoto is Hikone, most notable for it’s castle. While less grand than Himeji, it is also less crowded. Since Himeji is closed for construction, I’d recommend it as a second choice.
The castle is surrounded by a spiraling double moat, which feeds into the central pond of the beautiful gardens, which are preserved to appear the way they did during the castle’s prime. Perfect for an afternoon stroll.