The first turning is traditionally said to have taken place at Deer Park in Sarnath near Varanasi in northern India, to an audience of shravakas. It consisted of the teaching of the Four Noble Truths (Sanskrit: catvāry āryasatyāni) and the other elements of the Tripitaka – the Abhidharma, Sutrapitaka and Vinaya.
“After attaining enlightenment, Buddha gave his first teachings and gave a sermon on the first Wheel of Dharma. He gave this sermon in a deer park, Sarnath, in Uttar Pradesh, India.The first round of transmission took place at the Deer Park in Sarnath. Buddha went there with his five companions right after his attainment of enlightenment and gave them his first teaching. In it, he laid out the basic structure of his insight: the Four Noble Truths. These four are true sufferings, their true cause, their true stopping or cessation, and the true path or pathway of mind that leads to their true stopping and which results from it.”
From the Berzin Archives https://studybuddhism.com/en/advanced-studies/history-culture/buddhism-in-india/the-three-turnings-of-the-wheel-of-dharma