Burgruine Burgau, Castle ruin in Jena, Germany.

Burgruine Burgau comprises scattered stone foundations and wall remnants of a medieval fortification situated on a small hill above Jena. The visible structures include defensive embankments and building foundations that reveal the castle's former layout and protective design.

A castle at Burgau was first mentioned in 1305 as a Wettin seat, but the Lobdeburg family had founded it in the 12th or 13th century. From about 1480 it housed the Wettin double office of Jena-Burgau. It was destroyed in 1451 during the Saxon Fratricidal War and only partly rebuilt; in 1753 the dilapidated building was demolished down to its foundations.

The ruins reveal the layout of a medieval administrative center that served the region's rulers for centuries. Walking through the remaining walls, visitors can sense how the fortress was organized and used to control the surrounding lands.

The ruins remain accessible year-round without entrance fees, making them easy to visit from central Jena. The hillside location works well in dry conditions, so planning visits after good weather offers the best walking experience.

The Binderburg that Adolph Binder built from 1906 to 1910 was later rented out by the state housing administration after his family fled to West Germany in 1949, and it deteriorated during that period. After reunification the Binder family recovered the property and sold it in 2003 to the Jena physicist Michael Willsch, who began an extensive renovation largely done by his own labor. Parts of the building have since been used for events.