Its doors are still in use, though, at the cathedral St John Lateran in Rome. They’re the doors Julius Caesar walked through on the way to work…
And not exactly a building, but some Australian Aboriginal sacred sites have apparently been in continual use for tens of thousands of years:
In May 2020, in order to expand an iron ore mine, Rio Tinto demolished a sacred cave in the Pilbara region of Western Australia that had evidence of 46,000 years of continual human occupation
I’ve actually seen those doors up close (touched them even). St. John Lateran is a site that’s not exactly hidden, but is definitely overlooked in Rome. Really, really cool as churches go, and that’s saying something in Rome.
I suspect the answer is probably some sort of place of worship, but are there any temples in Asia that are older than the Pantheon?
https://en.wikipedia.org/wiki/Hōryū-ji/
Horyuji Temple, Ikaruga, Nara Prefecture, Japan. Built in 607 CE, burned down and rebuilt in 670 CE, widely considered to be the world’s oldest wooden building. Headquarters of the Shotoku sect, so still in use today.
https://en.wikipedia.org/wiki/Mundeshwari_Temple/
Mundeshwari Temple, in Ramharh Village, Bihar, India. Built in 635 CE. Still a pilgrimage site today.
https://en.wikipedia.org/wiki/White_Horse_Temple/
White Horse Temple, in Luoang, Henan, China was built in 68 CE. The Chinese and Indian governments are both working to preserve and renovate it, although I am not sure if it is an active temple, or just a historical site.