Śrīmad-Bhāgavatam · Text 2.5.42
Who is speaking and story frame
भूर्लोक: कल्पित: पद्भ्यां भुवर्लोकोऽस्य नाभित: ।
स्वर्लोक: कल्पितो मूर्ध्ना इति वा लोककल्पना ॥ ४२ ॥
bhūrlokaḥ kalpitaḥ padbhyāṁ
bhuvarloko ’sya nābhitaḥ
svarlokaḥ kalpito mūrdhnā
iti vā loka-kalpanā
Others may divide the whole planetary system into three divisions, namely the lower planetary systems on the legs [up to the earth], the middle planetary systems on the navel, and the upper planetary systems [Svarloka] from the chest to the head of the Supreme Personality.
Read Śrīla Prabhupāda's purport on Vedabase.io