SB 4.29.80
maitreya uvaca
bhagavata-mukhyo bhagavan
narado hamsayor gatim
pradarsya hy amum amantrya
siddha-lokam tato ’gamat
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The great sage Maitreya continued: The supreme devotee, the great saint Narada, thus explained to King Pracinabarhi the constitutional position of the Supreme Personality of Godhead and the living entity. After giving an invitation to the King, Narada Muni left to return to Siddhaloka.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Siddhaloka and Brahmaloka are both within the same planetary system. Brahmaloka is understood to be the highest planet within this universe. Siddhaloka is considered to be one of the satellites of Brahmaloka. The inhabitants of Siddhaloka have all the powers of yogic mysticism. From this verse it appears that the great sage Narada is an inhabitant of Siddhaloka, although he travels to all the planetary systems. All the residents of Siddhaloka are spacemen, and they can travel in space without mechanical help. The residents of Siddhaloka can go from one planet to another individually by virtue of their yogic perfection. After giving instructions to the great King Pracinabarhi, Narada Muni departed and also invited him to Siddhaloka.