Radnor Lake, an 85-acre reservoir built by the L&N Railway in 1914, sits at the centre of a 1,330-acre state natural area south of downtown — the wildest, most strictly protected green space in the city. The Class II designation means no jogging, no bikes, no pets on the perimeter trail; what you get in return is a near-guaranteed sighting of white-tailed deer, river otters, bald eagles, herons, and turtles.
Two main trails — the easier 1.4-mile lakeside path and the more strenuous Ganier Ridge Trail — circle the lake. Free entry. Parking fills early on weekends; come on a weekday morning or near sunset for the best wildlife viewing.