The Treasury, or 'Al Khazna' in Arabic, is the most magnificent monument carved by the Nabataeans. Its exceptional location at the Siq's entrance and its impressive height of 39.5 meters have given it unparalleled significance. The monument’s name comes from a local Bedouin legend that the pharaoh hid a treasure in the urn at the top, and you can see bullet holes from shooting at the urn to try to retrieve this treasure.

In reality, it is a mausoleum, likely used for funerary purposes. Archaeologists have debated the date and nature of this facade, with many believing it dates back to the reign of Nabataean King Aretas IV (9 BC–40 AD), rather than being a treasury as previously thought. Excavations conducted in front of the Treasury have confirmed this belief.

The Nabataeans decorated the facades of their tombs with funerary designs and symbols related to the afterlife and death. The façade of the Treasury reveals a Hellenistic influence, with six Corinthian capitals topped by a frieze of winged griffins and vases among scrolls. In the center of the façade is the goddess Isis, and she is surrounded by dancing Amazons (female warriors) with axes over their heads. A circular hole in the floor at the top of the steps, on the chamber entrance, was likely used for sacrifices by priests. In 2003, archaeologists from the Jordan Department of Antiquities made a remarkable discovery beneath Al-Khazna, uncovering three Nabataean royal tombs dating back to the end of the first century BC. This significant find sheds light on the historical significance and purpose of this iconic monument.