The B/ON-0809 Bunker KW Line BL4 Rixensaert is a World War II defensive fortification located in the province of Flemish Brabant, Belgium. It forms part of the KW Line (Koningshooikt-Wavre Line), a hastily constructed defensive barrier designed to halt a potential German invasion in May 1940. The KW Line was Belgium's last prepared line of defense before the Albert Canal and was intended to protect the approaches to Brussels and Antwerp.
This bunker represents the extensive military engineering efforts undertaken by Belgian forces during the early stages of World War II.