I am shooting numerous different types of long exposures of cityscapes. I want to know what is the best type of paper to print onto? I want to get the deepest blacks.
The deepest blacks
The deepest and richest colors, in my experience, come from super glossy papers. So, if you're in the darkroom, go for something like Fuji's RC Glossy crystal archive paper.
If printing at a lab, like mpix, do as @null says and go for the metallic paper.
If printing at home, I'm a super fan of Hahnemühle's Photo Gloss Baryta 320 paper. They also have an RC glossy that might work for your need, but I've no experience with it.
Metallic paper works well if the print will be illuminated properly to allow the illuminating light to bounce off the substrate and back through the ink absorbing layer to give it that "illuminated" from behind" look.
If the print is going to be hung without a decent source of direct lighting in a subdued lighting environment, it can look worse than regular glossy paper.