The Railway Tunnel is located in downtown Brockville and is a free attraction, although donations are welcomed. We stayed in an AirBnB in Brockville and were in walking distance to the tunnel.
The tunnel is quite a bit cooler than the outside air and a light sweater or raincoat is good to have during summer months. Water occasionally drips from above, but it wasn’t too bad.
You can walk the tunnel in about 30 minutes (one way). Inside the tunnel is a music and light show that lasts 90 minutes and repeats.
The tunnel is open from spring to fall and closes after a special show around Halloween.