Where to put the alien portal?

[Nik Hasta]

But the core of an existing nuclear reactor...? It’s not technically a solid object...

In fact in the next few years we should get the first industrial scale fusion reactors, and those things will have a core temperature of around 100,000,000 degrees (so around 7 times the temperature of the sun’s core).

I think that should do it.

That's a good one.

[bruceleegreyhulk]

The Large Hadron Collider

[Tami]

This idea isn't that far off from plot points where the hero has snuck onto the enemy invasion mother ship and has only a few minutes to adjust the location of the point of entry (portal or whatever) so as to spare the Earth from the worst of the invasion force. Though usually, that involves directing the invaders into the Sun or having them overshoot the coordinates to end up in Deep Space far from Earth, or crashing them into Jupiter, or something like that.

Being limited to just locations on Earth is much more difficult.