Marys Lake Dikes, Colorado-Big Thompson Project, are 2 dikes on the shoreline of Marys Lake, 2 miles from Estes Park, Colorado. There is a concession-developed campground accommodating 270 campsites, including both RV sites with utility hookups and tent camping sites, has been constructed adjacent to the site. Access is good. The reservoir has approximately 42 water surface acres, 175 land acres and 1 mile of shoreline. No boating is allowed. Primary recreation activities include camping, fishing, and picnicking. Primary fish species include rainbow trout. Facilities are closed in winter due to ice and snow.