One of Ontario’s most spectacular geological sights, the Cheltenham Badlands opens for the season next week. What are the Cheltenham Badlands? According to Ontario Heritage Trust, the badlands were first formed at the base of an ancient sea over 450 million years ago. History of the Cheltenham BadlandsSpanning 36 acres, the badlands were first occupied by Ancestors of the Mississaugas of the Credit for hunting, fishing, and foraging. Because The Cheltenham Badlands are at high risk of damage due to frequent public use, conservation work was performed to preserve the site and upgrade the surrounding trails.