Mosta Rotunda

Where it stands. The Rotunda sits directly on Mosta's main square, at the point where Constitution Street widens into Pjazza Rotunda, roughly seven kilometres inland from Valletta on the plateau of central Malta. There is no cathedral close, no protective forecourt, no approach avenue: the church rises straight out of a working town of shops, bus stops and parked cars, which is exactly what makes the first sight of it so disorienting. Its formal dedication is the Sanctuary Basilica of the Assumption of Our Lady, and Maltese speakers call it Ir-Rotunda tal-Mosta. Almost everybody else calls it the Mosta Dome. From the north the drum reads as a pale drum of globigerina limestone floating above flat rooftops; from the valley of Wied il-Għasel behind the town, it is the single object on the skyline.

The story behind it. The design came from Giorgio Grognet de Vassé, a Maltese architect of French descent who was better known in his lifetime for an elaborate theory that Malta was a surviving fragment of Atlantis. His proposal was frankly derivative — a circular hall under a hemispherical dome with a columned portico, transparently modelled on the Pantheon in Rome — and it beat a more conventional Latin-cross scheme by a rival. The foundation stone was laid on 30 May 1833. The genuinely remarkable decision came next: rather than demolish the existing parish church, a modest 1614 building attributed to the architect Tommaso Dingli, the parish built the new shell around and over it. Mass continued inside the old church for nearly three decades while the drum climbed over its roof. Only when the new structure was closed did the parishioners dismantle the old one and carry it out in pieces through their own new doors. The building was consecrated in 1871.

How it was built. Money was scarce and the parish was rural, so the work was done largely by the villagers themselves — quarrying, hauling and setting stone on Sundays and after the working day, under a succession of parish priests who kept the subscription alive across two generations. The dome has an internal diameter of about 37 metres, which for many years placed it third or fourth among the world's unsupported domes depending on how the list is drawn. It was raised without a full timber centering, an approach forced by the cost and scarcity of large timber on a treeless island: courses of dressed limestone were laid so that each ring closed on itself and stood on its own before the next went up. The walls beneath are enormously thick, which is why the interior feels like a chamber cut out of solid rock rather than a room enclosed by walls.

9 April 1942. In the second great blitz on Malta, a Luftwaffe bomb pierced the dome during an afternoon service with a congregation of roughly three hundred people inside. It struck the floor, skidded the length of the nave and did not detonate. Two further bombs glanced off the dome into the square without exploding. The bomb was defused and dumped at sea; a replica sits in the church museum behind the sanctuary, alongside photographs of the hole in the coffering. Whatever one makes of the word miracle, which the parish uses without hesitation, the event fixed this building in Maltese memory in a way its architecture alone never would have.

Inside. The interior is one enormous circular volume, ringed by six chapels and lit by the lantern and by windows cut in the drum. The dome ceiling is coffered in receding geometric panels picked out in blue, red and gold, a scheme that reads as far more assertive than the sober grey-gold stone of the exterior. The floor is laid in coloured marble; the high altar carries the Assumption; the six-column Ionic portico outside is flanked by two bell towers whose clocks, in the old Maltese fashion, do not agree — one is deliberately wrong to confuse the devil. Below the square lies a network of rock-cut air raid shelters dug by hand during the war, now open to visitors as part of the church's museum route.

Getting there and timing. Mosta is one of the best-served bus interchanges outside the capital, with frequent services from Valletta and from Sliema, and the Rotunda is a two-minute walk from the stops. Entry to the church for worship is free; the museum, sacristy and shelters carry a small combined charge, and modest dress is enforced. Mornings are quietest. The building is at its most theatrical in the two weeks before 15 August, when Mosta dresses the square for the feast of Santa Marija, hangs the street with banners and pastardi statues, and closes the celebration with one of the heaviest fireworks programmes on the island. Photographers should come in late afternoon, when low light rakes across the portico and the limestone turns from grey to honey.