Free
Grand Trunk Trail
A 3.2-kilometre trail on an old railway line, with the Sarnia Bridge as the highlight, a wide view south over the town and north into the countryside. Free.
Perth County, Ontario
St. Marys
A limestone town at the forks of the Thames and Trout Creek, with a trail over an old railway bridge, a riverside walk, a swimming quarry in summer, and the Canadian Baseball Hall of Fame.
Photo: The Sarnia Bridge on the Grand Trunk Trail over the Thames River in St. Marys, Robert Taylor from Stirling, ON, Canada, CC BY 2.0
St. Marys sits at the junction of the Thames River and Trout Creek, a short drive southwest of Stratford and northeast of London. It is built of local limestone, which is why people still call it Stonetown. The Grand Trunk Trail crosses the river on the old Sarnia Bridge, with a wide view over the town and the countryside.
The Riverview Walkway follows the Thames from downtown toward the quarries. The East Quarry is a flooded limestone pit run as a public swimming hole in summer. The West Quarry, reopened in 2026 after site work, is for walking, fishing and paddling, not swimming. Wildwood Conservation Area is a short drive east, on a reservoir. The Canadian Baseball Hall of Fame sits on Church Street, on land given by the cement company.
Outdoors and nature
Trails, lookouts, waterfalls, beaches and time on the water come first.
Free
Riverview Walkway
A 2.4-kilometre paved path from downtown along the Thames River toward the quarry, past remnants of the old mills. Free.
Free
West Quarry
A quieter former limestone pit, reopened in 2026 after site work, with views of the Thames and the quarry water. Fishing is posted as 1 April–30 November, dawn to dusk; paddling in human-powered craft is allowed in the same hours. Swimming is prohibited. Free.
Season Fishing is posted as 1 April–30 November, dawn to dusk; paddling in human-powered craft is allowed in the same hours. Swimming is prohibited (check before you go).
Free
Avon Trail
A long-distance hiking trail that starts in St. Marys and runs about 121 kilometres toward Conestogo, linking the Thames Valley and Grand Valley trails. Motorized vehicles, camping and fires are not permitted. Free.
Cheap
Wildwood Conservation Area
A reservoir and conservation area a short drive east of town, with hiking and cycling trails, picnic areas and a boat launch. A day-use or membership pass is required.
Season In the official non-camping season (19 October–30 November 2026), hours were listed as daily 8:30 a.m.–4 p.m.; a day-use or membership pass is required (check before you go).
Cheap
St. Marys Quarry
Canada's largest outdoor freshwater swimming pool, in a flooded limestone pit on the east side of town, with a cliff jump and rafts when water levels allow. A town admission applies.
Season Official 2026 swimming season Friday 26 June–Monday 7 September, 11 a.m.–7 p.m. daily; on Sunday 5 July the quarry was listed to open at 3 p.m. for the Stonetown Triathlon (check before you go).
Sights and attractions
Museums, landmarks and the places people come here for.
Free
Downtown St. Marys
A compact limestone downtown of shops and old stone buildings, a short walk from the river and the Town Hall. Free to wander.
Free
St. Marys Town Hall
The limestone Town Hall on Queen Street, the landmark of Stonetown, at the corner of Church Street. Free to look at from the street.
Free
Loop Trail
A 13-kilometre in-town loop past the Junction Station, the Baseball Hall of Fame and the quarry, useful as a longer walk or ride. Free.
Cheap
Canadian Baseball Hall of Fame and Museum
The national baseball hall of fame on Church Street South, with a museum and fields on the old cement-company land. Hours are seasonal.
Season The official plan-your-visit page listed the museum as open 10 a.m.–5 p.m. daily in July and August, and Friday–Sunday in September; visits from October to April are by arrangement (check before you go).
Markets, shops and festivals
Main streets, markets and the dates worth planning around.
Free
Downtown shops
Independent shops and restaurants in the limestone downtown, a short walk from the river.
Free
Queen Street shops
A few more shops and cafés along Queen Street, toward the Town Hall and the Church Street Bridge.
Book a tour or activity
Cruises, tours and experiences people book here. Each one goes to the operator's official page, and you can still add it to your trip.
St. Marys Quarry
Admission to the East Quarry swimming hole, in season. The Super Splash Waterpark is a separate ticket.
Season Official 2026 swimming season Friday 26 June–Monday 7 September, 11 a.m.–7 p.m. daily; on Sunday 5 July the quarry was listed to open at 3 p.m. for the Stonetown Triathlon (check before you go).
Canadian Baseball Hall of Fame and Museum
Admission to the museum on Church Street South. Hours are seasonal.
Season The official plan-your-visit page listed the museum as open 10 a.m.–5 p.m. daily in July and August, and Friday–Sunday in September; visits from October to April are by arrangement (check before you go).
Wildwood Conservation Area day pass
A day-use or membership pass for the reservoir, the trails and the picnic areas. Hours change with the season.
Part of our The Thames and the Avon guides.
Make it a weekend
Why stay the night
- The bridge trail and the river walk are a morning; the quarry or the conservation area is an afternoon that does not fit on the way through.
- The Sarnia Bridge is better at the end of the day, when the path empties and the river still holds the light.
- Stratford and London are close enough for a second day, but St. Marys itself is worth the night.
Nearby and worth the drive
Stratfordabout 20 min · Guide ↗
Theatre and the Avon River, about twenty minutes northeast.
Londonabout 40 min · Guide ↗A river city on the Thames, with a long paved trail and a year-round market, about forty minutes southwest.
Ready-made trips with St. Marys
Good to know
- Tourism: discoverstmarys.ca is the official visitor site.
- The quarries: Swim only at the East Quarry, in season, and only when it is staffed. Swimming is prohibited at the West Quarry. A town admission applies at the East Quarry; the Super Splash Waterpark is a separate ticket.
- Wildwood: A day-use or membership pass is required at the conservation area. Hours change with the season.
- We list only places we can check against an official source. Hours, seasons and prices change, so confirm before you go.
Photos on this page
Photo: The Sarnia Bridge on the Grand Trunk Trail over the Thames River in St. Marys, Robert Taylor from Stirling, ON, Canada, CC BY 2.0
Photo: The Thames River in St. Marys, Robert Taylor from Stirling, ON, Canada, CC BY 2.0
Photo: The swimming quarry in St. Marys, a flooded limestone pit, Robert Taylor from Stirling, ON, Canada, CC BY 2.0
Photo: Limestone downtown St. Marys, Ken Lund from Reno, Nevada, USA, CC BY-SA 2.0
Photo: St. Marys Town Hall, Ken Lund from Reno, Nevada, USA, CC BY-SA 2.0
Photo: The field at the Canadian Baseball Hall of Fame in St. Marys, Robert Taylor from Stirling, ON, Canada, CC BY 2.0