A caldera
yes it is true
Traditionally there are two different structures that can be left behind. Although both structures are a type of hole, there are general size requirements for each. If a smaller volcano suffers a collapse and the hole is less than 1 mile in diameter, it is called a crater. If a larger volcano collapses and the hole is larger than 1 mile in diameter, it is called a caldera.
The large hole at the top of a volcano is called a "crater." It is formed when explosions or collapses create a depression at the summit of the volcano.
Such a hole is called a fumarole.
It is called a volcano.
The name of the hollow landform, found at the top of the volcano is called crater.
it's called a crater.
Vent .
it is called a caldera a caldera is formed when a volcano erupts and it it such a big eruption that the volcano has no magma left in its chamber and since there is nothing left to support it, it caved in on itself.
If the Sun collapsed into a black hole, it would be about 3 kilometers in diameter.
It seems you are referring not to any collapsed star, but a black hole. The "event horizon" is the area from which nothing can escape.
It is called a crater.