In Schindler’s List (1993), a woman says a story:
The trains arrived and the people were driven out with clubs. They
were lined up in front of two big warehouses. One was marked "Cloak
Room," and the other "Valuables." And there they were made to undress.
A Jewish boy handed them pieces of string to tie their shoes together.
They shaved their hair. They told them it was needed to make something
special for U-boat crews. And then they were herded down a big
corridor to bunkers with Stars of David on the doors and signs that
said "Bath and Inhalation Room."
Why "down a" instead of "down from"?
Because it doesn’t mean down from.
As well as its use as an adverb, down can also be a preposition. From dictionary.com:
- in a descending or more remote direction or place on,
over, or along: They ran off down the street.
The meaning here is "along" – not necessarily in a downward direction.