Travelers step inside one of the most astonishing buildings of the ancient world—the Pantheon, Rome’s best‑preserved temple. Your guide leads them through the monumental bronze doors into the vast rotunda, where the world‑famous dome opens above them like the sky itself. They’ll stand directly beneath the oculus, the nine‑meter circular opening that lets sunlight—and sometimes rain—fall into the temple exactly as it did 2,000 years ago.