If you have a dream about a dark park, this is actually a good thing, you are thinking about all of the time that you have to enjoy yourself. A park is usually completely full of people all day long and it makes it hard for a person to enjoy themselves with the sounds of kids screaming, dogs barking, and joggers huffing filling the air with their breath. If the park is dark you have it all to yourself to enjoy it at your own pace, the way you want.
Dreaming of a dark alley symbolizes all of the things that you are most afraid to do, but it is telling you that it is a good thing you are not doing them because they will lead to danger and pain. If you have a dream in which you see a dark alley it is your mind telling you that you should stick to yourself and not go out of your shell too much or you might be putting yourself in danger.