The Murgia dei Trulli, with its communes of Martina Franca, Locorotondo, Cisternino, and Alberobello, is located in the Apulian interior at the upper part of the heel of Italy. Although trulli are scattered throughout the region, more than 1,500 of them are in the Monti and Aja Piccola quarters, on the western hill of Alberobello. This unique conical house form is significant in the history of architecture because it perpetuated well into the twentieth century a construction technique practiced throughout the northern Mediterranean since prehistoric times.
The name derives from truddu, Greek for “cupola.” The clustered stone dwellings of Alberobello, small by modern Italian housing standards, are built by roofing almost square or rectangular bases (although some tend toward a circle) with approximately conical cupolas of roughly worked flat limestone slabs, stacked without mortar in corbeled courses. These gray roofs, no two of which are quite the same, are normally crowned with a whitewashed pinnacle in the form of a sphere standing on a truncated inverted cone. Some are painted with symbols: astrological signs or Christian ones, and even some of older pre-Christian significance. As is often the case with vernacular architecture, geometrical precision is not a priority: nothing is truly right-angled, nothing truly plumb. Bernard Rudofsky describes the roof as a retrocedent wall, because it also encloses habitable space that is traditionally used for storage. Typically, the inside of the roof is a parabolic dome, formed by packing the gaps between the larger structural stones. The walls of the ground floor are thick enough—they can be up to 10 feet (3.27 meters) in older houses—to include alcoves for a hearth or cupboards, or even a curtained-off recess for a bed. Doorways are low, and the interior, though whitewashed, is usually quite dingy because the windows are small, possibly for structural reasons. Curved walls make furnishing difficult. More recent trulli, the last of which were built in the 1950s, are interconnected with others to gain more living space.
The oldest documented Alberobello examples date from the fifteenth century, coinciding with the foundation of a permanent agricultural community centered in the town. However, the essential building technique and the consequent house form are much older. The type, clearly related to the prehistoric nuraghi of Sardinia and the rather more sophisticated Mycenaean tholos, has been archeologically linked to both the nomadic pastoral Early Bronze culture and permanent agrarian communities in the Apennine region. Remarkably, similar constructions can be found in the middle of Scotland and on the west coast of Sweden.
A plausible and somewhat romantic tradition dates the development of trulli as the house form of Alberobello to a single historical event. It is said that in the eighteenth century the local ruler Count Girolamo II of Acquaviva compelled the peasant farmers to build their houses with mortarless stone roofs. Because drywall structures were tax-exempt, and because they could be (relatively) easily dismantled before the regular visits of inspectors from Naples, he chose this method of tax avoidance. Although the people were freed from his regulation by a decree from Ferdinando IV of Bourbons in May 1797, the house form persisted, perhaps because of rural conservatism. Trulli are no longer built by the traditional technique and in the traditional style, but some of the master builders are still living, and the craft skills have not yet been lost. After the mid-1950s the “romantic” trulli were noticed by tourists and real-estate agents, and that has been to the detriment of many of them. Since the inclusion of the Alberobello precinct on UNESCO’s World Heritage List in 1996, serious archeological study has been undertaken, and the old craft skills have been applied to an extensive restoration program.