I took a tour of Seattle, and the guides discussed Seattle going through a similar transition. Essentially the whole city was raised by one story. But the roads

I took a tour of Seattle, and the guides discussed Seattle going through a similar transition. Essentially the whole city was raised by one story. But the roads were done first, creating a sort of "waffle-like" city, where crossing the street as a pedestrian meant climbing a ladder, crossing the street, and descending the ladder on the other side. People were sometimes injured or killed by falling down the ladder, someone else falling down the ladder, or things falling onto them from street level. After the sidewalks were raised to match the streets, the underground sidewalks were kept open for a time, until (predictably) problems started with drugs and prostitution, etc. They were closed in the early 20th century but you can tour them today.