Mbh 2.21.2a

Vaisampayana said,--Thus saying those brothers of abundant energy, viz., he of the Vrishni race and the two Pandavas entered the city of Magadha. They then approached towards the impregnable city of Girivraja that was full of cheerful and well-fed inhabitants belonging to all the four orders, and where festivities were perennial. On arriving then at the gate of the city, the brothers (instead of passing through it) began to pierce (with their shafts) the heart of the high Chaityaka peak that was worshipped by the race of Vrihadratha, as also by the citizens and which delighted the hearts of all the Magadhas. There Vrihadratha had slain a cannibal called Rishava and having slain the monster made of his hide three drums which he placed in his own city. And those drums were such that once beaten their sound lasted one full month. And the brothers broke down the Chaityaka peak that was delightful to all the Magadhas, at that point where those drums covered with celestial flowers used to yield their continuous sound. And desirous of slaying Jarasandha they seemed by that act of theirs to place their feet upon the head of their foe. And attacking with their mighty arms that immovable and huge and high and old and celebrated peak always worshipped with perfumes and floral wreaths, those heroes broke it down. And with joyful hearts they then entered the city. And it so happened that the learned Brahmanas residing within the city saw many evil omens which they reported to Jarasandha. And the priest making the king mount an elephant whirled lighted brands about him. And king Jarasandha also, possessed of great prowess, with a view to warding of those evils, entered upon the celebration of a sacrifice, with proper vows and fasts. Meanwhile, O Bharata, the brothers unarmed, or rather with their bare arms as their only weapons, desirous of fighting with Jarasandha, entered the capital in the guise of Brahmanas.