Quinta da Regaleira is a historic estate located in the Sintra region of Portugal, near Lisbon. It was built in the early 20th century as a summer residence by wealthy Brazilian businessman, Antonio Augusto Carvalho Monteiro. The estate is known for its elaborate and ornate architecture, which is a blend of Gothic, Renaissance, and Manueline styles.

One of the most notable features of Quinta da Regaleira is its vast network of underground tunnels and wells, which were used for initiation ceremonies by secret societies. These tunnels and wells have become a popular attraction for visitors, who can explore them on guided tours.

In addition to its tunnels, the estate also features a palace, a chapel, and a lake, as well as a lush, verdant garden that is dotted with grottoes, fountains, and sculptures. The garden also has several walkways and paths that lead to different sections of the estate, offering visitors breathtaking views of the surrounding countryside.

Today, Quinta da Regaleira is considered one of the most important historical landmarks in Portugal, and it is a popular tourist destination for those interested in history, architecture, and the occult. The estate is also a UNESCO World Heritage Site, and it is open to the public for guided tours and self-guided visits.