342782
The Baltimore and Potomac Tunnel ( or B&P Tunnel ) is a double track , masonry arch railroad tunnel beneath Baltimore , Maryland .
 Baltimore, Potomac, Baltimore , Maryland
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Baltimore, Potomac, Baltimore , Maryland