On the eastern edge of Toronto is a natural wonder that's well worth a half-day visit. The Scarborough Bluffs are unique in North America, and their layers of sand and clay offer a remarkable geological record of the great Ice Age. Rising up to 105m (345 ft.) above Lake Ontario, they stretch out over 14km (8 3/4 miles). The first 45m (148 ft.) contains fossil plants and animals that were deposited by the advancing Wisconsin Glacier 70,000 years ago. The bluffs were given their name in 1793 by Lady Elizabeth Simcoe, wife of the first Lieutenant Governor of Upper Canada (Ontario); as she sailed to York, as Toronto was then known, she was reminded of the cliffs of Yorkshire.