The image shows one of the Initiation Wells on the Quinta da Regaleira Estate located near the historic center of Sintra, Portugal. It is classified as a UNESCO World Heritage Site. The estate consists of a palace and chapel, a luxurious park containing lakes, grottoes, tunnels and wells.
The wells resemble underground towers lined with stairs. In fact these towers were tunnels that connected two wells to each other. The larger well contains a 27-meter spiral staircase with several small landings. The smaller one also known as the ‘Unfinished Well’ contains straight stairs that connect a series of ring-shaped floors to one another.