This former rail tunnel has sat abandoned since 1900. It is now three-quarters buried by the earth, and half-flooded. Distinctive arrow imprints on the red and brown clay bricks indicate the presence of prison labourers in its construction. Prisoners serving terms with hard labour wore arrows on their uniforms to visually distinguish them from civilian workers, and they marked their handmade bricks with arrows, as a kind of self-portrait. Finding this tunnel was a team effort involving anecdotes from rail workers, hand-drawn maps of enthusiasts, and – finally – simply groping through thick vines in search of the source of faint sounds of trickling water. The entrances are completely obscured in dense overgrowth. The thrill of finding something so untouched for so long is indescribable.