Structural damage can easily be seen on its exterior surface. To ensure that the Hagia Sophia did not sustain any damage on the interior of the building, studies have been conducted using ground penetrating radar within the gallery of the Hagia Sophia. With the use of GPR (ground penetrating radar), teams discovered weak zones within the Hagia Sophia's gallery and also concluded that the curvature of the vault dome has been shifted out of proportion, compared to its original angular orientation.[182]