Non-invasive archaeology
The Muthiyangana Stupa is a large, dome-shaped Buddhist monument in Badulla, Sri Lanka. Tradition holds that its central relic chamber, or garbha, has been sealed since its initial construction. This presents a classic archaeological challenge: how to study a sealed structure without destroying it. The answer came from geophysics, specifically Ground-Penetrating Radar (GPR). GPR is a non-invasive technique that sends high-frequency radio waves into a structure. These waves bounce off different materials and voids at varying speeds, allowing scientists to create a map of the interior. The process is similar to medical ultrasound but uses electromagnetic waves instead of sound.
A GPR survey was conducted to peer inside the ancient brickwork of the Muthiyangana Stupa. The goal was to map the unseen architecture of the relic chamber. The equipment, typically consisting of an antenna dragged across the surface, collected data that revealed a complex internal layout. The radargrams showed clear anomalies and distinct shapes deep within the stupa's core. These data points were processed to generate 2D and 3D models of the hidden space, confirming the chambers and passages without drilling a single hole.
Ancient texts and modern signals
The GPR scan results were remarkable because they appeared to align with descriptions of stupa construction found in ancient Pali texts like the Mahavamsa. This chronicle, dating to the 5th century CE, details the engineering and ritualistic methods for building these sacred structures, including the precise layout of their internal relic chambers. These texts often describe a central chamber surrounded by smaller, systematically arranged cells for offerings and secondary relics. The GPR data from Muthiyangana revealed an internal geometry consistent with these ancient architectural blueprints.
The stupa itself is one of the 16 sacred Buddhist sites in Sri Lanka. Its history dates to the 5th century BCE, during the third and final visit of the Buddha to the island. A local ruler named Indaka is said to have requested a sacred object for worship, and the Buddha provided strands of his hair and drops of perspiration that had miraculously turned into pearls (Mukthaka Dhatu). King Indaka enshrined these relics and constructed the original stupa. Later, in the 3rd century BCE, King Devanampiyatissa expanded the structure and planted a sacred Bo Tree, a sapling from the original Jaya Sri Maha Bodhi in Anuradhapura. The use of GPR provides a modern lens to view this 2,500-year-old religious structure, connecting ancient textual accounts with contemporary scientific measurement.