It’s UN World Toilet Day, which means it’s time for some potty talk: Even Hong Kong’s humble public bathrooms have a long story to tell. The British constructed the first one back in the 19th century to keep people from urinating on the street.

Why underground though? To save space, of course! It is Hong Kong, after all, and even back then it was all development, development, development. Only a few of these subterranean WCs remain, and just one is still functioning to this day — head to the corner of Queen’s Road Central and Wellington to flush out the history yourself.

Consider donating to the UN World Toilet Day organization today, which raises awareness about the health, nutrition and environmental issues caused due to insufficient sanitation and lack of access to clean water.