Victor Vasarely was from Budapest and he MUST have been inspired by the architecture. As you can see here, there is a lot of repetition and rhythm in the architecture of Budapest. It's everywhere! There's more than in other cities I've visited. There were blocks and blocks of repetitive patterns.
Here's more in the floor of St. Stephan's Basilica on the Pest side. This could have been an inspiration for his circle paintings.
This view of the inside of the dome at St. Stephan's especially coincides with this series.