Tokorozawa's Yamaguchi Kannon is estimated to date back to the 9th Century, and if you're in the area the grounds are worth a visit. You're likely to spot the Kannon tower first due to its height and bright red color, but there are a number of different buildings to explore at the site.
Take your time when wandering around, and explore all of the little details. Some of the buildings have intricate wood carvings to appreciate, and there are a number of statues across the site. The ones wearing knitted red caps are jizo statues, dedicated to children who have passed.
In spring there are a number of sakura trees that bloom across the grounds, including one right by the Kannon tower itself.