Both Cherry Creek Reservoir and Chatfield Reservoir have dog parks. I haven't used either yet since I don't trust Apollo to come when he's off-leash. We're working on that! Also, I read in my neighborhood (Park Hill) newspaper that the City & County of Denver is looking to implement off-leash areas in existing city parks. They're going to start with one park in each of the four quadrants of the city, but haven't determined where for sure. City Park is one of the options. Also, I know that Wash Park was trying out an off leash area on a temp basis. The newspaper said people were lined up to get their dogs in. Good Luck!