Untere Burg, Water castle in Mechernich, Germany

Untere Burg Antweiler is a moated castle on the northeastern edge of the Eifel in the Antweiler district of Mechernich. Its outer wall stands on a 14th-century defensive wall and contains medieval keyhole loopholes; the present dwelling is the gate wing of the early 16th century, built against a much older corner tower. Inside, a Halfenhaus was added in 1728, and the main castle is enclosed by a ring wall once strengthened with towers.

The castle was probably founded in the 13th century by the advocates of Deutz Abbey and Dietkirchen Abbey to secure their rule over Antweiler. In 1345 the lords of Antweiler received jurisdiction from the Count of Jülich, forming the Unterherrschaft Antweiler. In 1488 the lords of Ahr acquired advocacy and lordship and split them between two lines around 1500; the younger line built the Obere Burg, whose Deutz advocacy returned to the Untere Burg in 1716.

The name Unterburg distinguishes it from the Obere Burg on the opposite bank of the Krebsbach; the two castles reflected the medieval division of land between the Deutz Abbey and the Dietkirchen chapter, whose advocates sat at the Unterburg. The restored 1846 bakehouse is still used monthly to bake bread.

The castle stands at the northeastern edge of Antweiler, a district of Mechernich; the Krebsbach, once meant to feed the moats, proved unreliable, so the ditches were dry by the 18th century and levelled by the 19th. The site is private property of the Freiherrn Raitz von Frentz, so the grounds are not open to walk through. The restored bakehouse of 1846 is used again: bread is baked there once a month.

The round tower of the outer bailey keeps a late Gothic helm split into two parts, and two heraldic chimneys from the castle survive: one was rebuilt at Burg Konradsheim, the other is kept in the forebuilding at Antweiler. The outer wall stands on the 14th-century defensive wall, and keyhole arrow slits remain in the masonry.