We are deep inside a larger Universe made of 7 material layers. That larger material Universe is called a Brahmanda that surrounds and encases our small universe in its middle.

Understanding our Brahmanda that surrounds and encases our small universe that is deep inside it.

Srimad Bhagavatam says there are millions of individual Brahmanda universes all coming from Maha Vishnu.

However, deep inside each of these Brahmanda universe is a smaller secondary universe, some of these secondary universes inside their Brahmanda are only 4 billion miles in diameter like ours.

Our "4 billion miles (500,000,000 Yojanas)" diameter of our universe with its 14 planetary systems is one of the smallest

Srila Prabhupada - ''We have to imagine that these universes (Brahmandas), which according to our limited knowledge are expanded unlimitedly, are so great that the "gross and subtle ingredients"—the five elements of the cosmic manifestation, namely earth, water, fire, air and sky, along with the total material energy and false ego—are not only within the universe but cover the universe in seven layers, each layer ten times bigger than the previous one.

In this way, each and every universe is very securely packed, and there are numberless universes. All these universes float within the innumerable pores of the transcendental body of Mahā-Viṣṇu.

It is stated that just as the atoms and particles of dust are floating within the air along with the birds and their number cannot be calculated, so innumerable universes are floating within the pores of the transcendental body of the Lord. For this reason, the Vedas say that God is beyond the grasp of our knowledge. '' Krsna Book 87

We CANNOT see from one universe to another, this is because our individual universe is surrounded and encased by 7 thick material layers that is our outer egg shaped universe called a Brahmanda.

So it is impossible to see the millions of other Brahmandas outside our inner universe (inside a massive Brahmanda) because of being surrounded by 7 thick material layers that only rare mystic yogis and advanced devotees like Arjuna can see and pass through.

So of course Krishna and Arjuna did not encounter such limitations we experience by the combination of these elements like earth, water, fire all gross elements as Bhagavad Gita explains.

Srila Prabhupada - ''The Lord is not visible to the eyes of ordinary men, those who are beyond the covering layers because of their transcendental devotional service can still see Him''. Krsna Book 87

We cannot see through our Brahmanda that surrounds and encases our small universe, Srila Prabhupada is clear on this

Srila Prabhupada - ''Lord Krishna and Arjuna crossed over the great region of darkness covering the material universes. Arjuna then saw the effulgence of light known as the brahmajyoti. The brahmajyoti is situated ''outside the covering of the material universes'', and because it cannot be seen with our present eyes, this brahmajyoti is sometimes called avyakta''. Krsna Book, 89

Srila Prabhupada - ''Each universe is covered by various layers of material elements (The 7 layers of the outer Brahmanda covering), and therefore although the universes are clustered together, we CANNOT see from one universe to another. In other words, whatever we see is within this one universe. In each universe there is one Lord Brahmā, and there are other demigods on other planets, but there is only one sun''.- Srimad Bhagavatam Canto 5 Chapter 21 Text 11, Purport:

Srimad Bhagavatam Canto 6 Chapter 16 Text 37

''Every universe is covered by seven layers—earth, water, fire, air, sky, the total energy and false ego—each ten times greater than the previous one. There are innumerable universes besides this one, and although they are unlimitedly large, they move about like atoms in You. Therefore You are called unlimited [ananta]''.

PURPORT

This verse describes the coverings of the universe (saptabhir daśa-guṇottarair aṇḍa-kośaḥ).

The first covering is earth,
the second is water,
the third is fire,
the fourth is air,
the fifth is sky,
the sixth is the total material energy,
the seventh is the false ego.

Beginning with the covering of earth, each covering is ten times greater than the previous one. Thus we can only imagine how great each universe is, and there are many millions of universes.

As confirmed by the Lord Himself in Bhagavad-gītā (BG 10.42):

athavā bahunaitena
kiṁ jñātena tavārjuna
viṣṭabhyāham idaṁ kṛtsnam
ekāṁśena sthito jagat

"But what need is there, Arjuna, for all this detailed knowledge? With a single fragment of Myself I pervade and support this entire universe."

The entire material world manifests only one fourth of the Supreme Lord's energy. Therefore He is called ananta''.