"Popular museum located in an old warehouse."
Is this a complete sentence?
I feel it could become one by changing it to "A popular museum, located in an old warehouse."
"Popular museum located in an old warehouse " looks like a telegraphic style of writing.
It may have been used in a newspaper headline, a touristic map, a brochure about places of interest, etc.
To turn it into a complete sentence I would add some more information and a main verb.
- "This is a popular museum located in an old warehouse" (or whatever you might want to add)
It can be converted into a full sentence by prefacing it with "It is a". A full sentence must have a finite verb. The located merely adds a past participle to the otherwise incomplete sentence.