A friend and I tucked into the rustic building at Jay Cooke State Park after a day of hiking. We were drawn by its brown-clapboard, dark-stone charm. Inside the structure — the River Inn Interpretive Center — picnic tables dotted the main room, but the fireplace of native rocks captured our attention. Little collections of, well, something, had accumulated near its top.

"Bird's nest?" I asked a park employee.

Actually, she replied, it was the work of mice.

The River Inn, I later learned, had been built by the Civilian Conservation Corps and is now on the National Register of Historic Places. Near hardwood forests and the St. Louis River, it has probably housed tiny scurrying mammals since its first days.

Resident mice are nothing compared with aging infrastructure, malfunctioning toilets and deteriorating bike paths. These are among the problems plaguing our state gems, according to the Minnesota Department of Natural Resources (DNR).

At a recent news conference at Itasca State Park, DNR Commissioner Tom Landwehr explained that the agency took a detailed review of its holdings, including state parks and trails. What it found surprised even them: The tally of all the needed repairs reaches $342 million, a result of years of delayed maintenance. This year Gov. Mark Dayton has asked for $33 million for repairs and renovations.

Among the units managed by the DNR are 75 state parks and recreation areas, 4,792 camping and lodging units, 2,898 miles of state trail and 33 water trails. That accounts for a lot of summer fun, so don't let the need for repairs keep you from heading to a park or trail this summer. Mostly, visitors won't notice the ancient pipes or leaky office roof.

If you see evidence of mice infiltrating a building, just chalk it up to nature, which you went to the park to experience anyway.

Send your questions or tips to Travel Editor Kerri Westenberg at travel@startribune.com, and follow her on Twitter: @kerriwestenberg.