Weingut I, Architectural heritage monument in Mühldorf Hart, Bavaria.

Weingut I is a half-built bunker in the Mühldorfer Hart forest near Ampfing. Its surviving section is a massive curved reinforced-concrete wall with vertical seams and a row of thin vertical reinforcements along the top edge. Below the wall, a recessed underside with horizontal beams forms a dark overhang above a gravel slope. A lattice crane stood in front during construction.

Approved by Hitler's order of 21 April 1944, Weingut I was built in the Mühldorfer Hart as a half-underground bunker for producing Messerschmitt Me 262 jet engines. Of 10,000 workers, 8,500 were forced labourers and Mühldorf camp inmates; over 3,000 died. Only 7 of 12 planned arch sections were finished, and the factory was never started. The US Army studied the concrete before demolishing all but one section in 1947.

The site is a listed monument, and occasional tours are led by a Catholic nonprofit group from Mühldorf. The codename "Weingut I" (Vineyard I) disguised a weapons project as an agricultural one. Of the 10,000 workers, 8,500 were forced laborers and inmates of the Mühldorf concentration camp network.

Access requires a permit from local authorities and visitors must follow marked paths through the area. The surrounding land is overgrown with vegetation, so wear sturdy shoes and appropriate clothing.

The US Army studied the bunker's construction methods before blowing up all but one of the seven finished arch sections in 1947. The surviving section still shows the vertical seams between the concrete panels and the row of thin reinforcement bars along its top edge.