The current structure of the mausoleum is divided into two decagonal orders, one above the other; both are made of Istria stone. Its roof is a single 230-tonne Istrian stone, 10 meters in diameter. Possibly as a reference to the Goths' tradition of an origin in Scandinavia, the architect decorated the frieze with a pattern found in 5th- and 6th-century Scandinavian metal adornments. A niche leads down to a room that was probably a chapel for funeral liturgies; a stair leads to the upper floor. Located in the centre of the floor is a circular porphyry stone grave, in which Theodoric was buried. His remains were removed during Byzantine rule, when the mausoleum was turned into a Christian oratory. In the late 19th century, silting from a nearby rivulet that had partly submerged the mausoleum was drained and excavated.