This invention relates to a marine riser tower (112, 114) for use in the production of hydrocarbons from offshore wells. The riser tower (112, 114) includes a plurality of fluid conduits, which may comprise production flow lines (P), gas-lift lines (G), water injection lines (W) and/or umbilicals (U). The conduits are supported in a single structure, and at least one of said conduits is provided with its own insulation within said structure.