An admirable work of hydraulic engineering with a long history, La Chiusa dei Monaci (Monks’ Lock) is the starting point of the cycle-pedestrian itinerary called the Sentiero della Bonifica “Vittorio Fossombroni” (Vittorio Fossombroni Land Reclamation Path), which from Arezzo reaches Chiusi and runs alongside the Canale Maestro della Chiana (Master Canal of Chiana) for 62 kilometres, leading to the discovery of the various artefacts that over the centuries served the complex reclamation of the valley. In the opposite direction, a link road starts from the lock, connecting the route to Ponte Buriano and the Arno cycle track.
La Chiusa dei Monaci is located on the western outskirts of Arezzo, reached after travelling along Via Calamandrei and turning right at the Chiani roundabout towards Via Molinara. Today it is immersed in a beautiful natural setting, ideal not only for outdoor walks but also for relaxation.
The first lock was already mentioned in documents dating back to 1115, but it was located slightly further downstream than the present one. It was built by the Benedictine monks of the Abbey of Saints Flora and Lucilla of Torrita di Olmo, who used it both as a “fishery” and to feed the fulling mills for wool processing and a grain mill with an artificial canal.
At a time when the Val di Chiana suffered from progressive swamping, the lock was also useful to regulate the flow of water. For the same reason, between 1339 and 1348, the Municipality of Arezzo promoted the lowering of the bed of what was called the “fossatum novum”, the first step of the future Canale Maestro. The old infrastructure was rebuilt. The excavation of the Chiana bed around La Chiusa dei Monaci continued under the control of Florence even after the definitive subjugation of Arezzo in 1384.
The floods that cyclically overwhelmed the artefact led to its dismantling again in 1532 and subsequent rebuilding in the following years. Other devastating floods, followed by reconstructions, are documented throughout the second half of the 16th century. So it was that at the end of the century, the people of Arezzo hypothesised a further enlargement of the canal, but the Florentines opposed this, fearing that a greater discharge into the Arno would have entailed a higher risk of flooding in their city.
Also in 1601 and 1603, floods caused damage to the lock and for this reason the monks obtained permission to move it a little further upstream, where the rock allowed for more solid foundations. In 1607, however, there was a new collapse and subsequent rebuilding. Also during the seventeenth century, the mathematician Enea Gaci suggested the total demolition of the structure, but Evangelista Torricelli, the official mathematician of the Grand Duchy of Tuscany since 1641, opposed the project.
In the mid eighteenth century, Leonardo Ximenes,engineer, was asked to develop a plan to lower it, but so as not to compromise canal navigability, nothing was done. In 1769, restoration work was started on the now dilapidated lock. In 1797 the Benedictines handed it over, after almost eight centuries, to the Order of the Knights of St Stephen, who already managed large agricultural properties in the valley on behalf of the Lorraine government. In those years, even Vittorio Fossombroni, supervisor of the Val di Chiana water department, recommended reducing its level.
New renovations affected the work in the nineteenth century. From 1829 to 1839, Alessandro Manetti, engineer, planned a considerable lowering and the construction of new sluice gates and a side outlet to regulate the flow of water. Manetti’s mighty stone and brick infrastructure is what we still admire to a large extent today, despite the war damage in 1943 that destroyed the right-hand regulator, later replaced with a bypass canal.
Immediately downstream from the Chiusa dei Monaci, we can admire from a privileged viewpoint the Mulino Romboli (Romboli Mill), one of those used to exploit the waters of the Canale Maestro for milling activities.