Nestled in the transition zone between prairie and hardwood forest, Glendalough offers a true respite from civilization. Crystal clear Annie Battle Lake is a 335-acre, non-motorized 'Heritage Fishery' that provides a tranquil fishing experience second to none. Special regulations sustain a steady supply of large sunfish, crappie, and the occasional walleye for the frying pan, and large bass for the camera. Near the pristine shores of this lake are a cart-in campground and canoe-in campsites, all free from the traffic and noise of traditional drive-in camping. Annie can also be the starting point for an exploration of the park by canoe or kayak on the connecting creeks. The restored historic Glendalough lodge on the north side of the lake details the park's history as a private retreat and game farm for the Minneapolis Tribune.

A paved bike trail loop and numerous hiking trails, including two interpretive trails, meander along five lakes, through rich woods and blooming prairies. Wildlife abounds year-round, and there are many observation decks along the trails. Trails are groomed in winter for skiing and snowshoeing. Picnicking and swimming is available on two sandy lakes.

Wildlife
Glendalough is home to abundant populations of white-tailed deer, raccoon, red fox, and smaller mammals. The park also offers excellent birdwatching for a variety of species of prairie, wetland, and hardwood forest birds. An active eagle nest and fresh beaver cuttings can be viewed from the park trails, and loons are common on the park's lakes. Wildlife observation blinds have been constructed and binoculars and birding kits are available for loan at the park.

History
The park is named after Gleann Da Loch (Glendalough) in Ireland, which means 'Valley of Two Lakes' in Irish. On Earth Day 1990, this largely natural and undeveloped property was donated to The Nature Conservancy. On June 10, 1992, the deed was transferred to the Minnesota Department of Natural Resources to become a state park.

Geology
Leaf Hills, like those in another state park, Glacial Lakes, is a term often used to describe the hills evident in Otter Tail County. The hills were created by glacial ice and meltwater deposits of sand gravel. Although the highest hills extend to 1800 feet above sea level, the hills in the park are much lower. The outwash drift in the Glendalough area is mainly sandy loam.

Landscape
One of the last large tracts of undeveloped lakeshore in western Minnesota (9.2 miles) lies within the park. The gently rolling topography is an excellent example of original landscape transition from prairie to northern hardwoods. This hilly, lake-strewn, and partially wooded countryside is an excellent setting for recreational activities.