Also known as Chak-Chak, Pir-e Sabz is the most holy, known, and visited pilgrimage site. This pir (another word for a Zoroastrianism pilgrimage site) is located inside a cave of a mountain near Ardakan City in Yazd Province. It is dedicated to Nikbanu, the princess of the last Sassanian Empire. She was escaping from the incoming Arab invaders, when they trapped her into the mountain. Praying for assistance, a part of the mountain suddenly separated her and the Arabs, and the rocks closed down between them. According to Zoroastrian beliefs, water that surface from the interior of the mountain are tears of the princess. In conclusion, Pir-e Sabz is a site for believers to grieve for the lost of the princess and the Persian Empire. It is also known as Chak-Chak because of the sound water makes when it trickles down.