Ashok Vatika (Hindi: अशोक वाटिका) was a garden in Lanka, the Kingdom of demon king, Ravana, as mentioned in the Vishnu Purana and Hindu epic, Ramayana of Valmiki, and all subsequent versions, including the Ramacharitamanas written by Tulsidas, where it finds mention in the Sundar Kand. The Vatika has garden houses around it, built by Vishwakarma himself
It was the location, where Sita, the wife of Rama was held captive by Ravana, after her abduction, also because she refused to stay in Ravana's palace, and preferred to stay under the Ashoka tree, hence the name. It was here that Ravana's wife Mandodari came to meet her and also where Hanuman met her for the first time, and identified himself with the finger ring of Rama.
Sita stayed at Ashok Vatika, till the end of the epic battle between Rama and Ravana, which resulted in the destruction of Ravana himself and most of this clan. Much of the Ashoka Vatika was destroyed by Hanuman, when he first visited Lanka, searching for Sita. Also destroyed was the Pramda Van at the centre of the Ashok Vatika.
Read more about Ashok Vatika: Present Location