Unduvap Full Moon Poya Day in Sri Lanka is a significant Buddhist holiday observed on the full moon of the month of Unduvap, which typically falls in December. This day celebrates several key events in Buddhist history:

• Arrival of the Bo Tree Sapling: It marks the arrival of a sapling from the sacred Bodhi Tree under which Lord Buddha attained enlightenment. This sapling was brought to Sri Lanka by Sangamitta Theri, the daughter of Emperor Asoka, establishing a link with Buddhism in India.

• Commemoration of Sanghamitta: Unduvap Poya honors Sanghamitta Theri's contribution to Buddhism in Sri Lanka. She played a crucial role in establishing an order of Bhikkhunis (nuns) and thereby contributed to the spread and establishment of Buddhism on the island.

On Unduvap Full Moon Poya Day, Sri Lankan Buddhists engage in various religious activities:

1. Observing Sil: Many devotees observe Sil, which involves keeping to a set of traditional precepts that include abstaining from certain physical comforts and participating in meditation, chanting, and listening to sermons.

2. Visiting Temples: People visit temples for worship and participate in religious ceremonies paying homage to Buddha, Dhamma (the teachings), and Sangha (the monastic community).

3. Offerings and Merit-Making: Buddhists make offerings such as flowers, incense, and lights at temples. They also engage in acts of generosity like giving alms to monks and sharing food with others as part of merit-making practices.

4. Reflecting on Teachings: The day is also used for reflection on Buddha's teachings, studying scriptures, and engaging with fellow Buddhists on discussions about Dhamma.

Unduvap Full Moon Poya Day serves both as a cultural occasion deeply rooted in Sri Lanka's history as well as a spiritual day for reflection, meditation, and religious observances among Buddhists across the country.