Barchessone Vecchio, National heritage farm building in San Martino Spino, Italy.

Barchessone Vecchio is a two-storey agricultural building with a 16-sided plan and a diameter of 28 metres, built in 1824 for horse breeding. Its upper floor is an octagonal dwelling supported by the innermost ring of pillars and a central column containing a spiral staircase. The building has been unusable since the 2012 earthquake.

The building was constructed in 1824 as a horse breeding facility and later served as a military equestrian center from 1883 until 1954. During both World Wars, it housed thousands of horses for military operations.

Locals call it the "basilica of the Mirandola valleys" because its sixteen-sided plan and ring of pillars recall early Christian churches. The nickname is tied to the building's former role in horse breeding, an activity documented in San Martino Spino since 1461, when Borso d'Este came to buy a foal. The octagonal keeper's dwelling on the upper floor is the only one of its kind among the area's barchessoni.

The building has been unusable since the 20 May 2012 earthquake (magnitude 5.9, epicentre about 6.5 km away) left it badly cracked; it was already damaged by a magnitude 4.7 shock on 17 July 2011. The environmental education centre "La Raganella" now runs from the Baita delle Valli, a temporary wooden structure beside it. Access to the interior is not possible while restoration is pending.

The upper octagonal dwelling rests on the innermost ring of pillars and a single large central column; a spiral staircase was cut inside that column, originally the only link between stable and dwelling. A brick lantern crowns the roof, and a pair of large rectangular windows with tilting shutters let hay be fed to horses from outside.