What's the word for an outdoor hallway?

Solution 1:

You could try "walkway". https://www.merriam-webster.com/dictionary/walkway and https://www.collinsdictionary.com/us/dictionary/english/walkway I'd suggest this as perhaps the best alternative. Speakers of any type of English would surely know what you meant.

Here are suggestions of a few synonyms for walkway: https://www.thesaurus.com/browse/walkway They include "loggia", "gallery", "passageway", and others. I would suggest that they sound a bit more elaborate that what you are describing, and that walkway seems best suited to the use you mention. Of these, I'd say "passageway" would be the best fit, although there's a possibility that it would imply walls on both sides of the passage: https://www.collinsdictionary.com/us/dictionary/english/passageway

Dictionary definitions of "hallway" suggest that it could fit what you're describing, but you'd clearly need to use the word "outdoor" with it (as you did in your question). https://www.collinsdictionary.com/us/dictionary/english/hallway