Arthur he came across the ruin of a circular temple, that had been demolished and built all around with walls without doors or windows right up to the very edge of the ruins. Perhaps it was the Temple of Aphrodite. It was accessible through the Catacombs. The Hierophant (one of the Six Guardians) guarded them in the Street of David.
The ancient marble stones were weather-worn and marble pillars were toppled. An empty round pedestal in the middle may had once held a statue or altar.
Behind the scenes
The Temple is displayed as the location of the Grail both in order to connect the legend of the Grail with the myth of the Sacred Cup of the Goddess, and also because it was the place where St. Helena found the True Cross while excavating.
In reality however, the Temple was demolished already from around 326 AD, and the Church of the Holy Sepulchre was built overlapping the Temple. The 'historical' King Arthur would find no ruins of a Temple, but the Church.
- "Around you is the ruin of a circular temple. Once there was a famous Temple of Aphrodite in Jeruselem. Perhaps this was it."