I'm Making My Own Solo D&D 3.5 Campaign

[aimlessPolymath]

Well Herlon is a major and important city in the country of Drivor. It has millions of people of all diverse and inclusive races.

That's a great answer for what people have heard about it! The next step is "what's the most important news of the day?". This question sets the stage for events, and more than one piece of news could be relevant. Some examples to provoke thought:
-How is its financial situation changing? Is a new market opening up? Is it losing trade? Is it stealing trade from another city? Is there a new tax or exemption that people are reacting to?
-How is the racial mix changing? Is one race increasing or declining recently? Are there tensions between two races?

Over time, an issue will resolve itself one way or another, changing the city. When that happens, look for the next thing to happen based on how the last one ended.

If you're not ready to answer that question, another thing you could do is go into more detail. Why is the city important? How do those races coexist successfully? Do they coexist successfully?