The Sidi Bashir Mosque, built around 1452, contains one of architecture's most persistent mysteries: two minarets, each three storeys tall, that when one is shaken, cause the other to vibrate — even though they are separated by a substantial archway.
The British colonial administration was so unnerved by reports of the minarets shaking that they reportedly dismantled one to examine its construction. They found nothing suspicious — and the remaining minaret promptly lost its ability to induce vibration in its neighbour.
Modern structural engineers believe the answer lies in resonance. The minarets sit on flexible joints that allow small oscillations. When one is set in motion, vibrations travel through the shared platform at a frequency matching the natural resonant frequency of the second minaret — sympathetic vibration, the same principle that causes a tuning fork to vibrate when its twin is struck.
What makes the minarets remarkable is that this was almost certainly intentional. Fifteenth-century Gujarati architects had no access to modern physics, but possessed an extraordinarily sophisticated empirical understanding of how stone behaves under load and motion — knowledge accumulated across generations of building in an earthquake-prone region. The minarets stand today in partial form; the caretaker will demonstrate the vibration for visitors.