That makes me wonder why Voldie didn't bury one of them in the middle of a mountain or something. Was it simply monumental, colossal arrogance? I mean, it was already fairly arrogant of him to only use historically significant artifacts, but there's a difference between being impressive and just being stupid. Is there, perhaps, some unbelievably important ritual that requires a Horcrux to perform? Do they need to be recharged every century or something?
If there isn't a pressing reason why anyone needs to be able to ever access them, then the question changes to how could someone so monumentally stupid become so deadly? I mean, if I was in Tom's shoes I would have hidden at least one of them at a random spot on the globe, maybe Tibet or Chile, in a hole a kilometer or so deep, which I would then cover with dirt. If I still felt the need to grandstand with the rest of my irreplaceable fragments of soul then, and only then, would I put them in locatable areas. Then again, I'm neither a raging megalomaniac nor insane from making Horcruxes, so perhaps it wouldn't occur to him to be careful.