The shores of glacial Lake Iroquois sat nearly 100 meters above the current level of its successor, Lake Ontario. When the Wisconsin glacier, which covered most of Canada, the upper US Midwest and New England, receded about 12,000 years ago the waters of the upper Lakes began to drain into the lower (and from them out to the Atlantic). Early Lake Erie flowed into Lake Iroquois at half a dozen locations across the Niagara Escarpment, with the spot that became the Niagara River eventually becoming the dominant waterway.
Roy Terrace, and its American counterpart Eldridge Terrace, marks the shores of Lake Iroquois when Niagara Falls was born. At that time the water draining from Erie only fell about 11 meters over the lip of the Escarpment. As the water fell it eroded the limestone and glacial material to carve out what we now know as the Niagara Gorge and Niagara River, with the Falls eventually receding to their present day location.
Named for the geologist Dr. Roy Spencer the Terrace is marked today by a monument erected by the Niagara Parks Commission at the entrance to Queenston Heights. From Roy Terrace a stairway gradually climbs towards Brock’s Monument. This spot sits on the Greater Niagara Circle Route recreational trail. To the south the trail heads down the Niagara Parkway towards the Falls while to the north it proceeds to wind down the Escarpment into the village of Queenston. This spot is mere meters from the Southern Terminus of the Bruce Trail.
You can find more on the history of Roy Terrace at Waymarking.com.