Best one we found was in the Denver area was in Golden right off of I-70. That would be a drive to get to Castle Rock, but it is close to the loop road that goes around the south side of Denver. The park is called Dakota Ridge. The website is www.essentialcoloradorv.com. It is a sister park to Elk Meadows in Estes Park. The sites are a little tight in places, but it has paved roads and paved sites. Have a good trip.