Complex sentence: The Standedge Tunnel Visitor Centre at the Marsden end of the tunnel is located in the former warehouse used for transshipment of goods from canal barge to packhorse between 1798 when the canal reached Marsden, and 1811, when the tunnel opened.
Split into simpler sentences: The Standedge Tunnel Visitor Centre is situated at the Marsden end of the tunnel. It is located in the former warehouse used for transshipment of goods from canal barge to packhorse during the period between 1798 when the canal reached Marsden, and 1811, when the tunnel opened.