The historic centre of Sintra in Portugal is classified as a World Heritage Site and it’s easy to see why. The area is famous for its elegant palaces and historic estates, with one of the most stunning of these being Quinta da Regaleira. The enormous estate was previously owned by millionaire Antonio Augusto Carvalho Monteiro and houses a palace, chapels, lakes, parks and fountains. The most stunning features of all though are the two 27 metre deep (90 ft) Initiation Wells. These incredible pieces of architecture are basically inverted towers that are linked together through underground passageways. The wells actually never served as water sources but instead feature spiral staircases with small landings that were used for ceremonial purposes. The deepness of the wells and the maze of underground tunnels just beg to be explored!