Inquisitor's Palace, Birgu

Where it sits. The Inquisitor's Palace stands on Main Gate Street in Birgu, a couple of minutes' walk inside the town's land front and about the same from Vittoriosa Square. From the outside it is deliberately unremarkable: a long stone façade with a Baroque doorway, wedged into a street of ordinary houses, giving away almost nothing about its size. The building runs deep, around two courtyards, and occupies far more ground than the frontage suggests.

The story behind it. It began as the Castellania, the law courts built in the early 1530s when Birgu was the Order of St John's capital and needed a place to try civil and criminal cases. When the Knights moved across the harbour to Valletta after 1571 the courts went with them, leaving a substantial public building empty in a town that no longer had a use for it. In 1574 the Holy See sent Pietro Dusina to Malta as inquisitor and apostolic delegate, and he took the vacant courthouse as his seat. It remained the headquarters of the Maltese Inquisition for 224 years, until the tribunal was abolished when French forces occupied the island in 1798.

A three-cornered power struggle. The inquisitor was never simply a prosecutor of heresy. He was also the pope's permanent representative on an island ruled by a sovereign military order under nominal Spanish suzerainty, and his tribunal offered anyone in Malta an avenue of appeal that bypassed both the Grand Master and the bishop. That made the palace a political instrument as much as a religious one, and the friction between the three authorities runs through two centuries of Maltese history. The post was also a career step of the first rank: sixty-two inquisitors served here, many went on to become cardinals, and two — Fabio Chigi and Antonio Pignatelli — were later elected pope.

What you actually see today. The visit works its way down the social scale and then back up, which is what makes it memorable. The piano nobile holds the inquisitor's own apartments and audience rooms, panelled and painted, with the coats of arms of successive occupants. The tribunal room is arranged as it was used, with the inquisitor's raised seat, the scribe's table, and a doorway cut deliberately low so that anyone entering had to bow. Below and behind are the prison cells, small stone rooms with barred windows onto a yard, and their walls carry the most affecting thing in the building: graffiti scratched by prisoners over generations — ships under sail, crosses, names, dates, tallies of days. There is a torture chamber, though the tribunal used it far less often than popular imagination assumes; the records show most cases ended in penance rather than anything worse. A kitchen, a chapel, cisterns and servants' quarters complete the circuit.

Afterwards. Once the tribunal was gone the building was put to a series of unglamorous uses — military hospital, officers' mess, convent — which is one reason so much survives: nobody had the money or the motive to modernise it. It opened as a museum in 1966 and has been the National Museum of Ethnography since 1992, which means part of the display is given over to Maltese religious and domestic life: ex-votos painted by sailors who survived storms, devotional objects, festa material, and the material culture of popular belief. That combination — the machinery of an inquisition upstairs and the folk religion it policed downstairs — is a genuinely intelligent piece of museum planning.

Why it matters. Inquisitors' palaces were built across southern Europe and South America, and almost all of them were destroyed, gutted or converted beyond recognition. This one survived largely intact and is the only example anywhere that is open to the public as a museum of itself. For anyone interested in how early modern institutions actually worked — the paperwork, the rooms, the hierarchy expressed in ceiling heights — it is more instructive than any number of restored cathedrals.

Getting there and timing. Take the passenger ferry from Lascaris Wharf below Valletta to the Birgu marina and walk up into the town, about seven minutes uphill, or arrive by bus at the land front and walk in through the gates. The museum is run by Heritage Malta; a combined ticket with other national sites is usually available and is worth doing if you are also visiting Fort St Angelo, five minutes away at the end of the promontory. Allow an hour and a quarter. There are stairs throughout and no lift, and the cell block involves uneven floors and low headroom. The building stays cool even in August, which makes it a sensible place to be between noon and three when the streets outside are unwalkable. Combine it with St Lawrence's church and the maritime museum on the waterfront for a compact half day.