Misty rain refers to Mao Mao rain like smoke, like a poem and a dream.
So misty rain is an image here, expressing a dreamlike feeling.
There are two kinds of landscapes in the old town here. One is from the public's point of view, referring to ancient cities or cities with many historical accumulations.
But there is another kind that is common in the article, that is, from the point of view of the person who said this, he may have nostalgia or affection for his "ancient" city.
For example, the city you live in is not an ancient city, but after you left your hometown for many years, you found that your hometown has changed a lot. Although it is more prosperous, it is no longer the home you remember. Looking back, you can say that you are better at reading misty rain in the old city.
In short, the old city gives people the feeling of simplicity, peace or the precipitation of years, while misty rain adds a bit of obscurity, which is generally used to describe things in memory.
Pure hand tour, hope to adopt.