At the heart of Sintra's Quinta da Regaleira, a breath-taking initiation well celebrates Portugal's unique historical connection to the mysterious Knights Templar.

Near the manicured gardens and hilltop villas of Sintra, Portugal, lies the fairytale estate of Quinta da Regaleira. Protected within a Unesco World Heritage landscape, Quinta da Regaleira is a postcard-perfect mix of Gothic, Egyptian, Moorish and Renaissance architecture. But it’s what lies beneath the palace’s gardens that truly sets the estate’s design apart. A pair of wells, called the Initiation Wells, spiral down deep within the earth, like inverted towers. The wells were never used to collect water. Instead, they were part of a mysterious initiation ritual within the Knights of Templar tradition.

Quinta da Regaleira has had many owners over the decades, but it was António Augusto Carvalho Monteiro, one of the wealthiest men in Portugal at the turn of the 20th Century, who made the estate what it is today.

Carvalho Monteiro had a deep interest in – and was quite possibly an initiate of – the Knights Templar, a Catholic military order with roots dating to the early 12th Century. While the group is believed to have disbanded 700 years ago, certain groups, like the Freemasons, revived the medieval group’s rituals and traditions centuries later. With architect and set designer Luigi Manini, Carvalho Monteiro created a property brimming with pagan and Christian symbolism between 1904 and 1910. The property’s wells, located in the expansive gardens that Manini also designed, served as the starting point in Templar candidate initiation ceremonies.

It is believed that Templar initiations at Quinta da Regaleira began with candidates entering one of the Initiation Wells blindfolded. Holding a sword close to their heart, they would descend nine flights of stairs – a number that represents the nine founders of the Templar order. Once reaching the bottom of the well, the candidate would walk into a dark labyrinth where they would symbolically and literally find their way up towards the light. If they were able to make back through the well tower and into the sunlight, initiates would walk across stones in water to reach the chapel, where they would then be welcomed into the brotherhood.

While Templar initiations no longer take place at Quinta da Regaleira, visitors are welcomed trace the footsteps of candidates past, experiencing this ode to Portugal’s hidden myths and history firsthand.

(Video by Fernando Teixeira and Izabela Cardosa; text by Emily Cavanagh)

This video is part of BBC Reel's Hidden Histories playlist.

Join more than three million BBC Travel fans by liking us on Facebook, or follow us on Twitter and Instagram.

If you liked this story, sign up for the weekly bbc.com features newsletter called "The Essential List". A handpicked selection of stories from BBC Future, Culture, Worklife and Travel, delivered to your inbox every Friday.