Mihintale and the Ambasthale Dagoba are at the top of a prominent hill near Anuradhapura, and you reach them by climbing a lot of ancient stairs. (A dagoba/stupa is a Buddhist center of worship or meditation.)
Speaking of: at one point, I gave Sterling a milk box to drink in the backpack. When he was (mostly) done with it, I held on to it as we climbed, keeping an eye out for a trash can. Instead, I got stalked by an aggressive monkey who very much wanted that milk box. I was determined to stand my ground, be a responsible tourist, and throw the box away in the trash, but there was no trash can anywhere and the monkey was getting increasingly brave. Finally, a passing Sri Lankan woman told me (in German!) that it would be safer to just give the monkey the milk box. So I did. And we all watched, fascinated, as it retreated up into a tree and tore open the milk box with its hands and teeth. Sometimes you wonder what your young children will remember about a certain vacation; I think my kids will remember THAT.
We headed back down as the sun set, the end of a perfect visit. Thinking back, there was nothing about the dagoba/stupa structure itself that was amazing. What made this site my favorite was the effort required to reach it, and the rewarding views from the top in a peaceful, worshipful atmosphere. We had decided to go there almost on a whim, even though it was out of the way, and I'm so glad we did.