Well now! Steampunk with zombies and pirates, and a certain amount of historical fact to boot? Welcome to turn of the century Seattle.
IRL, Seattle suffered a devastating fire in the late 1890s which tore through the lumber constructed Pioneer Square, its original downtown. There was also the issue of frequent rain-induced flooding, due to the steep coastal shoreline. So the civic leaders swapped out timber construction for masonry, and rebuilt, streets and all, on the top of the original buildings. The lower levels acted as storm drains when needed, and the buildings were still in use for awhile, streets illuminated by glass bricks in the sidewalks above. They were closed off in the early 20th century due to fears of harboring bubonic plague, but one can still visit them on tours. (I have, and it’s fun in an eerie sort of way.)
In Boneshaker, the initial event is instead man-caused, by Dr. Blue’s Incredible Bone-Shaking Drill Engine. But not only is Seattle left to deal with the catastrophic damage, but the destruction has unleashed a foul low-lying yellow Blight Gas. High walls are constructed around the affected area, but there are plenty who still live inside, in high buildings and underground safeholds. And then there are those who don’t exactly fall into the living category, and they are a creepy lot indeed.
Dr. Blue’s widow, Briar Wilkes, has fled for a hard-knock life right outside the city walls with her teenage son, Zeke. But when he starts having questions that she is reluctant to answer, he makes his way under the wall to find out for himself. She tries to follow, but an earthquake collapses that entry point, and Briar is forced to deal with those who have reasons to stay inside in order to rescue her son.
This was wild, and all the tiger-mom points for Briar.