Down a narrow, cobblestone lane in the heart of the northern Portuguese city of Porto stands a centuries-old monument to Jewish valor and ingenuity. Several years ago, workmen renovating a four-story medieval structure at 9 Sao Miguel street in the old Jewish quarter discovered a false wall on the ground floor. Upon removing it, they entered a large and dusty room containing an unusual recess carved into the facade. Local historians and experts were quickly called in, and they identified it as the holy ark of a secret synagogue, one that had served Portugal's "hidden Jews" after the forced conversions to Catholicism of 1497. That was the year when the Portuguese monarch, King Manuel I, had cruelly ordered the Jews of his realm to be dragged to the baptismal font. Despite the trauma they endured, many of the Anousim (Hebrew for "those who were coerced"), as they came to be called, continued to practice Judaism covertly, while outwardly professing to be Catholics. At great risk to themselves and their families, they struggled to preserve the faith of their forefathers down through the centuries. For a visitor to Porto, the ark is a tangible sign of the Jewish presence which once flourished here and throughout the rest of the country. Indeed, as I gazed at the niche in the wall and ran my hand slowly over the smooth stone, I marveled at the courage that it took to defy the Inquisition and its henchmen. Yet that is precisely what untold numbers of Anousim (whom historians often refer to by the derogatory term "Marranos") in Portugal and elsewhere chose to do. In 1506, thousands of them were murdered in the streets of the capital in what came to be known as the Lisbon Massacre. Then, in 1536, the Portuguese Inquisition was established, and it went to work hunting down those suspected of being crypto-Jews. From 1540 through the late 18th century, tens of thousands of Anousim were hauled before church tribunals, which did not hesitate to burn at the stake those whom it found guilty of following the Laws of Moses. But even in the face of such ruthless persecution, the Anousim stubbornly clung to their Judaism. What a tribute it is to their determination that they went to the trouble of building clandestine houses of worship to remain faithful to the God of Israel. BUT SECRET SYNAGOGUES are not the only tangible relics of Portugal's Jewish past that are being uncovered these days. Even more intriguing, and exciting, is the process of discovery that is under way as increasing numbers of Portuguese Anousim are seeking to reconnect with their Jewish heritage. Last Wednesday, on the top floor of Porto's grand Mekor Haim synagogue, I sat in a room with some 60 Portuguese Anousim, a number of whom have formally returned to Judaism. They sang Hebrew songs, recited traditional blessings before and after eating, and spoke movingly about their personal stories. One, whom I will call Miriam, is a researcher at the local university. She recalled how her grandmother clandestinely lit candles every Friday evening in a hidden corner of their home, far away from the prying eyes of neighbors. And despite growing up in an overwhelmingly Catholic society, neither she nor her siblings had ever been baptized, carrying on a tradition dating back generations in her mother's family. "Here, in the synagogue, I truly feel at home," she told me. A few months ago, Porto's small Jewish community held elections to pick a new president. And while such balloting is commonplace throughout the Jewish world, the outcome in Porto was anything but. For the first time, one of the local Anousim, Prof. Jose Filipe Ferrao, was selected to head the community. As a child, he remembers, his parents warned him never to count stars in the sky, lest the neighbors suspect them of practicing Judaism. That, after all, was how Portugal's crypto-Jews would determine when the Sabbath had concluded. Twenty-three years ago, while a graduate student in Paris, Ferrao went to a synagogue for the Friday night service welcoming the Sabbath and had a transformative experience. "I will never forget it. I felt as if I had known the songs and the prayers all my life, as if it was an intrinsic part of me," he said. He spent the next two decades learning more about Judaism and drawing closer to the faith that the Inquisition had tried, yet failed, to snuff out. JUST TWO YEARS ago, Ferrao, along with 15 other Anousim from Porto, came to Jerusalem and underwent a formal return to Judaism before a rabbinical court with the help of Shavei Israel, the organization that I chair. They are now at the core of Porto's Jewish revival. Indeed, throughout the Spanish- and Portuguese-speaking world, there are hundreds of thousands of Anousim, and possibly more, who still carry the Jewish spark within them, longing to come back. Israel and the Jewish people owe it to them and to their ancestors to recognize the anguish and suffering they have endured and to facilitate their return. Specifically, there are a number of steps that can and should be taken to help the Anousim, including publishing more material on Jewish topics in Spanish and Portuguese, sending teachers and rabbis to reach out to them and raising awareness about their existence to smooth their reintegration into the Jewish community. From Spain and Portugal to Brazil to the southwestern United States, the number of Anousim coming out into the open is surging, even as so many young Jews are sadly leaving the fold. Now, more than ever, we must swing open our collective door and enable them to come back home. The writer is chairman of Shavei Israel (www.shavei.org), a Jerusalem-based group that assists "Lost Jews" seeking to return to the Jewish people.