GIS and drone survey show Lima's riverside 'wall' was a flood-control structure

Researchers from Universidad Científica del Sur and Universitat Politècnica de València have concluded that masonry in Lima's 'Parque de la Muralla' belongs to tajamares, riverbank retaining structures, not the colonial city wall. The open-access study appeared in Built Heritage on 21 September 2026.

The team flew a DJI Mavic 2 Pro at 150 m over 10.255 km² of the historic centre, producing a 3.74 cm ground sampling distance orthomosaic in PIX4Dmapper. Historical maps and a 1944 aerial photograph were georeferenced in ArcMap 10.8 using affine transformations only, with RMSE and a metric equivalence error as quality checks.

The reconstructed wall measured 10,683.86 m, close to the viceroy's reported figure of about 10,867 m, indicating the circuit never closed along the river. Reconstructions closing it measured 12,763 m. Remains showed stone 'teeth', a trapezoidal section and mixed masonry typical of repaired river defences. The authors note that the structures have not been dated.

Why it matters: The study shows how drone photogrammetry and strictly controlled georeferencing can test long-accepted heritage claims against measurable evidence. The method transfers to other historic cities, including African colonial-era towns where plans may be symbolic rather than metrically accurate.