Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 8: Daśaratha Decides to Perform the Aśvamedha Sacrifice
Text 1.8.15

सरय्वाश्चोत्तरे तीरे यज्ञभूमिर्विधीयताम्।
शान्तयश्चाभिवर्धन्तां यथाकल्पं यथाविधि॥

sarayvāś cottare tīre yajña-bhūmir vidhīyatām
śāntayaś cābhivardhantāṁ yathā-kalpaṁ yathā-vidhi

sarayvāḥ ca = of Sarayū; uttare = on the northern; tīre = bank; yajña-bhūmiḥ = a sacrificial arena; vidhīyatām = prepare; śāntayaḥ ca = the performances of rituals that destroy obstacles to such auspicious activities; abhivardhantām = increase; yathā-kalpam = in the prescribed order; yathā-vidhi = and as per scriptural regulations.

Prepare a sacrificial arena on the northern bank of Sarayū. Increase the performances of rituals that destroy obstacles to such auspicious activities in the prescribed order and as per scriptural regulations.

From this, it is understood that Ayodhyā was on the southern bank of the Sarayū. Yathā-kalpam indicates that one should carry out the sacrificial rituals in the prescribed order, for the Kalpa-sūtras describe the order [of performing various activities in a sacrifice] [3].

[3] kramas tu kathyate kalpe (Bhāguri).