The biography of Jesus, as detailed in the Gospels, contains a puzzling gap. After 12-year-old Jesus’s visit to the Temple in Jerusalem in Luke 2, in the following chapter Jesus reappears at “about 30 years of age.” What happened in that roughly 18-year time interval, which spans Jesus’ adolescence and young adulthood, is one of the most intriguing mysteries in history. It has spawned both scholarly inquiries and scores of popular books, the latter filled with theories that Jesus disappeared to join a secretive monastic sect in the Judean desert or ventured to India, Japan, Tibet or Britain.

Here are some of the explanations that have been offered over the years for Jesus’ missing years:

Jesus stayed in Nazareth. The simplest, least complicated scenario for Jesus’ missing years is that he stayed in his hometown, probably working at his father Joseph’s trade of carpentry and studying Jewish scripture, and became the head of the household after Joseph’s death. As Addison Dare Crabtree noted in his 1884 book The Journeys of Jesus, sons generally were required to learn their fathers’ trades, Mark 6 seems to support this, by recounting how when Jesus began to teach at the local synagogue, people were astonished that a familiar person from their community had such wisdom. “Is not this the carpenter?” they supposedly asked. As Crabtree opined: “it seems that Jesus grew to manhood’s estate working with his hands, while he acquired wisdom and knowledge from the great book of nature, open all about his mountain home, and also a perfect understanding of the written revelation as handed down by the Hebrew fathers.”

Jesus became a disciple of John the Baptist. In his book Rabbi Jesus: An Intimate Biography, Bruce Chilton casts doubt on the notion of Jesus staying in his hometown, because the gospels don’t mention him trying to marry and start a family, “which is what a village youth who simply stayed home would have done.” Instead, Chilton believes, Jesus didn’t return home at age 12 after visiting the Temple, but instead remained and eventually became a follower of John, who trained him in his philosophy. “Jesus had a rebellious, venturesome spirit,” Chilton argues. “He did not become a passionate religious genius by moldering in the conventional piety of a village that barely accepted him.”

Jesus had a rebellious, venturesome spirit.

Jesus traveled to the Himalayas, and trained with mystics there. Back in 1894, a Russian named Nicholas Notovitch published an account of his trip to the secluded Himis monastery in Tibet, where he claimed to have been shown a 3rd Century AD manuscript explaining Jesus’ lost years. During that time, it supposedly related, Jesus—or Issa, as the monks called him—trained with yogis in India, Nepal and Tibet. But Notovich’s story began to unravel after skeptics visited the same monastery and spoke to the head monk, who reportedly called it “Lies, Lies, Lies, nothing but Lies!” Notovich subsequently admitted that he had not been shown a single manuscript as he originally claimed, but by then, his credibility was shredded. Nevertheless, other visitors to Tibet later claimed to have seen the mysterious manuscript as well, and variations of Notovitch’s explanation for Jesus’ lost years have resurfaced again in recent years.

Jesus went to Qumrān, and studied with the Essene sect. Some have speculated that Jesus left home to Qumrān, on the edge of the Dead Sea, where he supposedly became a member of a monastic community. Modern interest in Qumrān surged after the 1947 discovery of the Dead Sea Scrolls, a collection of ancient religious texts, in a nearby cavern. In the popular 1950s book The Lost Years of Jesus Revealed, Charles Potter capitalized upon the sensational sensation surrounding that archaeological find to make the case that both Jesus and John the Baptist were Essenes, whose philosophy embraced a view of oneness of everything in the universe with God, and espoused nonviolence. Potter argued that Jesus either wrote or was influenced by an apocalyptic book called The Secrets of Enoch.

Jesus traveled to Britain. Dennis Price, in his book The Missing Years of Jesus: The Extraordinary Evidence that Jesus Visited the British Isles, notes that British legends claim that Jesus visited Britain as a young man. It’s a scenario that William Blake alluded to in verse: “And did those feet in ancient time /Walk upon England’s mountains green? And was the Holy Lamb of God / On England’s pleasant pastures seen?” Among other evidence, Price notes that before the Roman invasion of Britain in AD 43, a British tribe, the Dubunni, minted coins bearing the name of a mysterious person named Eisu, who apparently rose to prominence around 30 AD—around the time that Jesus was crucified. British author, philosopher and critic Colin Wilson, who reviewed the book, noted that Price’s hypothesis, while fascinating, has one major flaw: “There is no actual evidence that Jesus visited Cornwall, Stonehenge or Glastonbury.” In a 2008 film, And Did Those Feet, Scottish minister Gordon Strachan proposed a theory similar to Price’s.

Jesus traveled to Japan. In a 2013 Smithsonian magazine article, writer Franz Lidz described his trip to Shingo, a tiny village in northern Japan, which attracts 20,000 tourists a year by billing itself as Kirisuto no Sato (“Christ’s Hometown”). Local legend holds that Jesus came to Japan at age 21, landing at the port of Amanohashidate, and became a disciple of a Buddhist master near Mount Fuji, learning Japanese language and culture as well., before returning to Judea by way of Morocco at age 33. As Lidz recounts, locals also believe that Jesus escaped from the executioners in Jerusalem and eventually made his way back to Japan. There, he supposedly fathered three children and died at the age of 106, and was buried in a hillside grave that has become a tourist attraction. The origins of the myth are a bit murky. Some suggest that the seeds of Christianity were planted in Shingo by missionaries who visited the village before Christianity was banned in 1614, and may actually have been the ones buried on the hillside. The Jesus-goes-to-Japan narrative itself, though, reportedly didn’t surface until the 1930s, when a set of supposedly ancient documents were mysteriously found—only to disappear again during World War II, as the story conveniently goes.

But all of these disparate theories have one thing in common: They’re conjecture, based upon creative interpretation of the thinnest of evidence. Until someone discovers more solid proof of what Jesus went and what he did in those years, it seems likely that Jesus’ missing years will continue to remain an intriguing mystery.