This is probably one of the most bizarre phenomena I've ever seen. Many Hong Kong families employ live in Philippino domestic helpers (aka maids). During the week, they are completely invisible as they work inside homes. But on every Sunday, their day off, they come out in the tens of thousands and occupy every single public space there is -- public parks, plazas, pathways, to socialize with their fellow countrywomen. Since they are live in maids, they don't have anywhere else to go to socialize.
They even hold entertainment events for themselves... in the middle of the financial district!