If you're looking for a fun swimming hole to visit in Ontario this summer, good news: the St. Marys Quarry officially opened for the season a few weeks ago. The quarry is located in the town of St. Marys and is approximately a 2.5-hour drive west of Toronto. The abundance of limestone sourced from the quarry even earned St. Marys the nickname "Stonetown." For 80 years, the swimming hole has been a go-to spot for anyone seeking to cool off in fresh, crystal-clear waters. If you're more of a thrill seeker, consider leaping off the limestone cliffs that line the swimming hole, because nothing says summer like a bit of adventure.