Columbia subject headings:
Fortification--Germany--History.
Valckenburgh, Johan van, approximately 1575-1625.
Harvard subject headings:
Fortification--Germany--History.
Military engineers--Germany--Biography.
Valckenburgh, Johan van, approximately 1575-1625.
Princeton subject headings:
Architecture--Germany.
City planning--Germany.
Valckenburgh, Johan van, 1575-1625.