Gull Lake Rotary Park is the easy green space near downtown, with a beach, lawns, summer concerts, and room to slow down away from the wharf. It also holds one of Gravenhurst's less expected stories.
During the Second World War, the former Calydor Sanitarium grounds became Camp 20, an internment camp for German prisoners of war. The visible remains are modest, but the information kiosk and surviving traces make the park more than a lakeside picnic stop.