Aerial view of fort IV Optyń/ Luftansicht Werk Optyn
B – Barracks/ Kasemattkorps
KK – Gorge caponier/ Kehlkoffer
K – shoulder caponier/ Schulterkoffer
R – open rampart gun position/ offene Geschützstellung am Wall
Bt – armoured battery/ Panzerbatterie
T – traditore battery/ Traditor Batterie