Who built the underground Victorian times?

The underground structures during Victorian times, particularly in London, were primarily built by the Metropolitan Board of Works and later the London County Council. These included sewers, tunnels, and the early underground railway systems, such as the London Underground, which began operation in 1863. Engineers like John Fowler and Joseph Bazalgette played significant roles in designing and constructing these vital infrastructure projects, addressing the challenges of urbanization and public health.