The city of Denver's website is comprehensive and you can find almost everything you need to know about conducting business with the city on their website. DenverGov.org If you can't find something you are looking for on their website, they make it extremely easy to contact them.
You can submit a request online 24/7 at Denver's website.
For Emergencies Call 9-1-1.
Address: 201 West Colfax Denver, CO 80202