One of the people in my network is an anthropologist who has studied and lectured on the changing form of kitchens over the decades, and also my sister has a business designing kitchens, so I've been paying close attention to kitchens for the last several years.
Here's a good example of a traditional Korean kitchen, through the middle sliding doors which you can tell are lower down than the other doors. Kitchens used to be below floor level, because the ovens were also used to heat the floor in the rest of the house.
And here's a more contemporary one from the late 20th century, when women's work was kept out of view in the household.
Here's a toilet that hopefully wasn't originally located there (although I've seen an
active kitchen with a toilet).