Can you guess what it is?

I was a bit flummoxed at first. And I'd seen where it came from.

But I don't think I've ever seen anything quite like this before.

It is a smell trap - to be placed into the drains in your bathroom floor. The idea is that they are open at the top but closed at the bottom; the outlet is through a small hatched door three-quarters of the way up which can be lifted by water; so, until they're nearly full, these little cylinders are closed, and provide a seal against the horrible smells (and so on) that may be lurking in the pipes below.

This is very necessary in China, because all the drains go into the same pipe - yes, the sewage pipe - and the Chinese are  still largely unfamiliar with the simple miracle of the S-bend. (5,000 years of history, and they haven't discovered plumbing yet!)

Unfortunately, of course, this being China, the design is seriously flawed: the hinged door sticks, is not easily lifted by the rising water; it gets clogged by hair and dirt in less time than it takes to have a shower; and even when clean, unobstructed, and with its hinge moving freely, the opening is far too small to allow the ready passage of the volumes of water produced by your average shower nozzle. Result: the bathroom floods every time you have a shower; and you have to remove the traps at regular (daily!) intervals for maintenance, which allows the disgusting drain stench to escape into your apartment.

Ah, China.