Omurtag (or Omortag) (Bulgarian: Омуртаг; original Greek: Μορτάγων and Ομουρτάγ) was a Great Khan (Kanasubigi) of Bulgaria from 814 to 831. He is known as "the Builder". In the very beginning of his reign he signed a 30-year peace treaty with the neighboring Byzantine Empire which remained in force to the end of his life. Omurtag successfully coped with the aggressive policy of the Frankish Empire to take Bulgaria's north-western lands and suppressed the unrest among several Slavic tribes. He made administrative reforms which increased the power and the authority of the central government. His reign was marked with a strong development of Bulgarian architecture with a number of significant construction projects.