Quinta da Regaleira is the early-20th-century Romantic estate built 1904–1910 in the valley below Sintra town by Italian architect Luigi Manini for the Brazilian-Portuguese millionaire António Augusto Carvalho Monteiro. Nicknamed "Monteiro dos Milhões" — Monteiro of Millions — Carvalho Monteiro made his fortune in Brazilian coffee and precious stones, then spent a decade turning a modest 17th-century estate into an esoteric theatre of symbols.
The palace itself is the entry point, but the site's fame belongs to what lies beneath: the Initiation Well, a 27-metre-deep inverted tower with a spiral staircase of nine landings and 135 steps, never used for water — built as a ceremonial descent. At the bottom, a compass rose with the Templar cross and Carvalho Monteiro's arms. The well connects to an underground tunnel network that winds past grottos, waterfalls, and the smaller Unfinished Well, emerging at Leda's Grotto and the estate's artificial lakes.
The iconography is deliberate and dense — Freemasonry, Knights Templar, Rosicrucianism, alchemy, and Dante's Divine Comedy are all legible in the architecture to those who know to look. UNESCO inscribed Regaleira, along with Pena Palace and the other Sintra monuments, as the Cultural Landscape of Sintra in 1995 — the first European cultural landscape ever listed.