Columbia subject headings:
City walls--Spain--Madrid--History.
Excavations (Archaeology)--Spain--Madrid.
Madrid (Spain)--History.
Harvard subject headings:
City walls--Spain--Madrid.
Excavations (Archaeology)--Spain--Madrid.
Madrid (Spain)--Antiquities.
Madrid (Spain)--History.
Walls--Spain--Madrid.
Princeton subject headings:
Madrid (Spain)--Antiquities.
Walls--Spain--Madrid.