Either a big longer distance, more elevation gain, or short but quick elevation gain that gets your heart pumping.

Walker Home Ruins via Parmalee, Meadow, and Castle Trail Loop - Mount Falcon Park

(really anywhere in Mt Falcon Park is beautiful, a lot of connecting trails here)

Eagle's View Trail Loop - Reynolds Park

Red Rocks and Morrison Slide Loop - Red Rocks/Matthews Winters

Lookout Mountain Trail (you can drive up it, but if you want the adventure take the hike LOL)

Independence Mountain Trail - Pence Park

Don't let the low mileage fool you, it climbs about 800 feet within 1 mile. It kind of hurts lol.

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