According to Srimad Bhagavatam, portals, gateways or wormholes to other worlds or realities, do exist.

According to Srimad Bhagavatam "Portals" or gateways into other realities in the material creation do exist. 

Portals through space-time to other planetary systems do exist on this Earth global sphere, however, it is nonsense to believe other worlds or planetary exist inside our Earth globe. 

Therefore the Hollow Earth theory is silly nonsense.

Even going down just 7.5 miles, the temperature is over 375 degrees centigrade, so at least human life down there would not survive. 

However, there are "portals" in various places on this planet, like the Himalayas, that do lead to other worlds in the lower and higher planetary systems "outside" our Earth Globe.

Arjuna also visited one of these "portals" in the Himalayas. 

These "portals" do NOT lead into the earth's interior where it is way too hot, these portals (often called wormholes) are pathways that actually lead to other higher and lower planetary realms both subtle and gross "outside" of our earth Globe as said above.

There is no such thing as a hollow Earth.

Another name for these "portals" is "wormholes" that lead to many other places in the material universe OUTSIDE our earth globe.

And even outside our small universe and its surrounding Brahmanda it is encased in, and into another Brahmanda. 

Although this portal travel to other Brahmandas is very rare and only achieved by great devotees like Naradha Muni and Arjuna etc.

Sarva-gatah means life is everywhere, this means there IS life even in the earths very hot core like bacterial life. 

Although on the Sun planet there is also life but exists on a subtle dimensional level within a material bodily vessel that allows life to flourish on the Sun, or the Moon etc, compared to our gross realm on our Earth.

Therefore we should also understand that all the hellish planets exist UNDER the Earth globe, and "NOT INSIDE" the Earth globe according to Srimad Bhagavatam.

This is important to understand.

On the earthly planetary level, our earth globe is NOT hollow, there is a mantle made of Lava and molton rock that begins 7.5 miles down. 

The Russians drilled into the Earth globe at the Kola Superdeep Borehole on the Kola peninsula to 7.5 miles down and could not go any futher due to the heat from the inner mantle.

Man cannot go any deeper because the temperature is 375 degrees C and as one goes deeper into the mantle it reaches nearly 6000 degrees C.

In otherwords there is no such thing as Hollow Earth but "portals" do exist as seen in painting below.