
Cherry Creek With a designated side for pedestrians on foot for part of the trail, you won't have to fight with the cyclists for room if you're pushing a twosome. Cherry Creek is a no frills urban concrete trail that will satisfy your need for a smooth surface to punch out your 3, 4 or even 10 mile run. There are also other convenient side trips off this trail if you want to mix it up some days.
Sloan's Lake -You really can't beat the lovely trails of Sloan's lake, and the spectacular view of the mountains from the park. The view itself is worth it, and there's a small playground for the youngsters on the North side of the park. I suggest parking on the east side, jogging clockwise and ending at the park, with a 1/4 mile cool down near the end of your jog for a solid 3 mile run. The concrete trail circles Sloan's Lake for about 3 miles, with at least 2 potty breaks available. Worth the drive if you don't live nearby, and several mommy's stroller groups meet here.
Highline Canal The HL canal is technically a 66 mile trail that starts near the mountains by Waterton Canyon through three counties and seems to go forever, but there's one length of the trail that's unbeatable. This "Best" is due to the mile markers, the wide trail, soft and very smooth gravel surface, and adequate parking. I suggest starting at Dekoevend Park, part of the South Suburban length of the trail, which lasts 18 miles. Quite often if you go early in the AM or on a Saturday morning, there will be water stations set up by running groups who don't mind if you have a cup or two of their water. A lovely place to train for the half marathon or 5k.