Can a spell cast inside a globe of invulnerability be counterspelled?

Question

If a spell caster is inside a globe of invulnerability and they try casting a spell, can somebody outside of the globe use counterspell to block their attempt to cast that spell? I had though it would not be possible, but the globe of invulnerability only protects creatures and object while counterspell is arguably targeting the spell itself.

Answer 1

No, it can't

Counterspell "interrupt[s] a creature" - if that creature is within a Globe of Invulnerability then Counterspell "has no effect on them."

Answer 2

Nothing inside the globe can be affected by Counterspell even if you cast it at higher levels

Although your exact question has not been answered on Sage Advice, I believe the answer concerning how Dispel Magic applies to the Globe, applies just as well:

dispel magic could affect the barrier created by globe of invulnerability, but not anything inside the barrier

which aligns with the description of the Globe:

Any spell of 5th level or lower cast from outside the barrier can’t affect creatures or objects within it, even if the spell is cast using a higher level spell slot

So you're better off trying to use Dispel Magic to get rid of the Globe first.