An adit.
In North America, the horizontal or sloped entrance to a mine is called a "Portal".
Portal more specifically refers to the portion of the shaft visible from the outside of the mine.
In some areas, the Portal portion of a horizontal shaft is called the "Drift Mouth" or "Drift Portal" as this shaft leads into a "Drift Mine".
With a vertical shaft, that portion would be called a "Collar".
For an ordinary strato volcano (cone-shaped) the throatwould be the name.
But for some shield volcanoes, the caldera may be the name of the magma pool whilst it is close to the surface.
Its called a shaft, whether it is a horizontal or vertical opening. An adit.
The flap over the wind pipe entrance is called the epiglottis.
The opening of a forest is called a glade.
glottis
its south of brimhaven dungeon - at the entrance of the gold mine.
The Underworld. Another answer may be AVERNO
A mine entrance is technically an 'adit'
Adit
Adit
Adit
The opening of the mine was at the entrance of the complex. "It's mine!" Yelled the toddler. Mine came first followed by Jessica's.
A cave entrance is commonly referred to as a cave mouth or cave opening.
An entrance or passage. Specifically: The nearly horizontal opening by which a mine is entered, or by which water and ores are carried away; -- called also drift and tunnel., Admission; approach; access.
The horizontal entrance is called a portal. If there are two portals, then you call the excavation a tunnel. If there is only one, it is call a drift or adit.
The flap over the wind pipe entrance is called the epiglottis.
A horizontal entrance to a mine is known as an adit.
The paseo is the opening procession or parade
adit