The Brockville Tunnel is a historic 525-meter (1,730-foot) railway tunnel in Brockville, Ontario, constructed between 1854 and 1860, and it stands as Canada's first railway tunnel, providing access to the riverfront from the Ottawa Railway. Once a working railway line, the tunnel is now a popular free tourist attraction with modern LED lighting, informative panels, and a dynamic light show that highlights the tunnel's 19th-century architecture and the calcite mineral formations created by dripping groundwater.