Join Groundwork Lawrence for a brisk hike through Lawrence’s “hidden jewel,” Den Rock Park. The Den Rock Park conservation area is a 120- acre wooded preserve that includes walking trails, a granite rock face, scenic overlooks, beaver ponds, “The Marsh”, vernal pools and access to the Shawsheen River and its floodplain forest. Well behaved dogs on leashes are welcome. Participants should wear sturdy shoes or boots and dress for the weather. The park entrance is located on Rt. 114, across from the North Andover Mall.