Quinta da Regaleira is a historic estate in Sintra, Portugal built in the early 1900s. The owner, Carvalho Monteiro, designed the 4-hectare estate with enigmatic buildings inspired by symbols of alchemy, Freemasonry, the Knights Templar, and Rosicrucians. The estate features Roman, Gothic, Renaissance, and Manueline architectural styles. It includes tunnels, grottoes, fountains, and an aquarium built into rocks. The estate is now open to the public and classified as a protected historic site.