Green Lakes State Park in Fayetteville, just east of Syracuse, is named for its two glacial lakes whose water is a striking blue-green. The colour comes from an unusual phenomenon: the lakes are meromictic, meaning their deep and shallow waters never mix, leaving suspended calcium carbonate particles that scatter light. Fewer than 100 such lakes exist worldwide.
Round Lake and Green Lake sit in a glacial plunge basin surrounded by old-growth upland forest. A trail loops around Green Lake in about an hour, mostly flat, with views down through the clear water to the chalky bottom. Swimming is allowed at the designated beach on Green Lake in summer.
The park also has an 18-hole golf course, picnic areas, and campgrounds. In winter, cross-country skiing and snowshoeing take over the trails. It's a 15-minute drive from downtown Syracuse.