This is a loop that we run quite often. From my house on the east side of town it's just a shade over 30 miles. It follows Hwy 19 to the Bluff Road north of Vermillion. You follow the Bluff Road until the Meckling Road. Staying on Meckling Road until it ends (turns into gravel) and you come back into town on Timber Road.
A few little rises but a good flat fast course for when you are looking for a speed workout. Other than the initial stretch on Hwy 19, very quiet country roads. Biggest concern may be an occasional dog popping out for a look see on the Bluff Road.