A passage through a hill is typically called a tunnel. It is an underground passageway that cuts through the hill, allowing for easier transportation or access.
An abruptly raised hill is called a bluff. It is a steep cliff, bank, or promontory.
Through... what? It's still a cave, unless so short relative to its diameter that it can be called a Rock Arch. There are caves that pass right through hills, sometimes because the land surface has been eroded down across the passage (common in the tropical karst of SE Asia). In places a riverhas cut a cave down below its a valley floor then popped out again somewhere down-valley, leaving the intervening part of of its valley high and dry. I can think of quite a number here in Britain. Through-trip caves are quite common in some areas, where a system has several entrances. In fact the water has eroded its way all the way to the rising even if the lower reaches are not humanly-enterable in size.
Yes, El Dorado is reportedly near a famous hill called Chimborazo. Legend has it that El Dorado, a mythical city of gold, is located near this hill in South America.
Yes, the Northwest Passage is real. It is a sea route that connects the Atlantic and Pacific Oceans through the Arctic Archipelago, north of the Canadian mainland. However, for much of history, it has been impassable due to thick ice. In recent years, with the melting of Arctic ice due to climate change, the Northwest Passage has become increasingly navigable.
Please provide the passage for review.
A tunnel
A passage through a hill ; underground, is called a TUNNEL. However, a passage between two hills (surface) is a VALLEY. A passage between two hills is dependent on its width. If the hills are low and far apart, then it is a VALE. However, if the hills are high and close together then it is a GLEN or RAVINE, or GORGE.
It is a tunnel.
A trail
To enter through the back secret passage of the hill.
A valley.
bone marrow.
Plasmodesmata.
osmosis
it could be a valley or a gorge
The Northwest Passage Apex;;;
Smoothing an object's shape is called streamlining. It is used for improving passage through air as well as water.