What is the importance of the City of Yarrow in the novel, Frogkisser!?

The City of New Yarrow represents the turning point for Anya, as seeing the poverty and lawlessness of the City she is finally convinced to wage the greater war against the Duke. The setting is also a symbol of the power of evil magic and sorcery generally. Nix describes the City first in Chapter 5 when Anya considers going there to get her ingredients, “long ago the High Kingdom of Yarrow had fallen apart when Yarrow the City was inundated by a tidal wave, and the entire royal family and government drowned” (52 - 53). The tidal wave was an accident of the last King who was dabbling in evil magic. The result is the dissolution of the High Kingdom and the All-Encompassing Bill of Rights and Wrongs under the Only Stone, and the creation of the new city called New Yarrow built on the ruins of Yarrow the City, as well as new canals and rivers as opposed to streets. Anya later flies with her friends to the city because she needs to break into the meetinghouse of the League of Right-Minded Sorcerers to get the rest of her ingredients to make her lip balm, and the City of New Yarrow is the setting for Chapters 24 - 29. In order to navigate they get a boat and otter guides to take them to the meetinghouse. On the way Anya sees the trash and filth of the river and city, and helps some starving orphans. It is at this point that Anya says, “Someone [italicized] should do something” and realizes that someone is her, and that something is restoring the kingdom (280). They steal the goods they need from the meetinghouse, Shrub also stealing the Only Stone, and they run to a rooftop where the magic carpet flies them back to Trallon Forest.