Srimad-Bhagavatam: Canto 8 - Chapter 1 - Verse 14
Sanskrit:
आकाशगङ्गया देव्या वृतां परिखभूतया ।प्राकारेणाग्निवर्णेन साट्टालेनोन्नतेन च ॥ १४ ॥
ITRANS:
ākāśa-gaṅgayā devyāvṛtāṁ parikha-bhūtayāprākāreṇāgni-varṇenasāṭṭālenonnatena ca
Translation:
The city was surrounded by trenches full of Ganges water, known as Ākāśa-gaṅgā, and by a high wall, which was the color of fire. Upon this wall were parapets for fighting.