Features of a quality gym Numerous training options, a well-designed space and facility, top-notch exercise gear, a digital fitness platform, and personal training services. Green Door Fitness is a local fitness center in Denver following all state and local mandated safety procedures. We have a variety of trainers on site to help you get the most out of your work out, expand and try new things, and more. From a basic class to the lead up to a rowing competition, we will take you to a new level on our ergs!