The land that is now Quinta da Regaleira had many owners through time. But in 1892 it belonged to the Barons of Regaleira, a family of rich merchants from Porto, when it was purchased that year by Carvalho Monteiro for 25,000 réis.
Monteiro wished to build a bewildering place where he could gather symbols that would reflect his interests and ideologies. With the assistance of the Italian architect Luigi Manini, he designed the 4-hectare estate with its enigmatic buildings, believed to hide symbols related to alchemy, Masonry , the Knights Templar , and the Rosicrucians .
The architecture of the estate evokes Roman, Gothic, Renaissance and Manueline architectural styles. The construction of the current estate commenced in 1904 and most of it was concluded by 1910.
The estate was sold in 1942 to Waldemar d'Orey, who used it as private residence for his extensive family and ordered repairs and restoration works for the property. In 1987 the estate was sold once again, to the Japanese Aoki Corporation and ceased to serve as a residence.
The Aoki Corporation kept the estate closed to the public for ten years, until it was acquired by the Sintra Town Hall in 1997. Extensive restoration was promptly initiated throughout the estate, which opened to the public in June 1998. Cultural events also start to be organized in Quinta da Regaleira. In August that year, the Portuguese Ministry of Culture classified the estate as "public interest property".
The Regaleira Chapel is a Roman Catholic Chapel stands in front of the palace's main façade. Its architecture is akin to the palace's. The interior of this Roman Catholic temple is richly decorated with frescoes, stained glass windows and lavish stuccoes. On the frescoes are represented Teresa of Ávila and Saint Anthony, as well as other religious depictions. The floor contains representations of the armillary sphere of the Portuguese discoveries and the Order of Christ Cross, surrounded by pentagrams. Despite its size, the chapel has several floors.
The park contains an extensive and enigmatic system of tunnels, which have multiple accesses including the grottoes, the chapel, the Waterfall Lake, and the "Leda's Cave" beneath the Regaleira Tower. Their symbolism has been interpreted as a trip between darkness and light, death and resurrection.
Water is a frequent element in the estate. Two artificial lakes and several fountains were designed in the property. One of the most interesting and extravagant features of the estate is the Aquarium, built as if it were naturally embedded in a rock. Once one of the most important naturalist presences in Regaleira, the Aquarium is nowadays in poor state of conservation.