The Dhamek Stupa of Sarnath, India.
The Archaeological Survey of India, and many alike, claim this to be the location where Buddha first encountered the five Parivajrakas and delivered the First Sermon.
Built in approximately 500 CE, the Dhamek Stupa is a huge cylindrically shaped stupa (Buddhist commemorative monuments which traditionally usually house sacred relics associated with Buddha), and is about 44m tall, with a diameter of 29m. Around it are 8 niches which are thought to have once contained images. Below these niches is a section of beautifully carved ornamentation, which remains partly preserved today, and highlights the high skill level of stone artisans of the Gupta period.
A Chinese traveler who visited Sarnath in 638 CE by the name of Hiuen-Tsang records seeing the Dhamek Stupa, and observing over 1,500 priest there.
The first photo is by Dennis Jarvis, and remaining two, Ramón.