Oberburg
Oberburg (the Upper Castle) lies just north of Kobern-Gondorf, and is just a ruin today.  Perfect, as these are the kind of castles I prefer to find.  Oberburg is perched on top of a rocky crag above the northern edge of the town, with river side slopes incredibly steep.

Oberburg was built in the 900s and was an outpost to assist in guarding the trade route along the river.  It was later joined by the Niederburg (Lower Castle) in the south part of the town in the 1100s.  Just behind the Oberburg is the Matthias Kapelle, or St. Matthew's Chapel, dating from the 1300s.  Supposedly the head of Matthew the Apostle was retrieved during one of the Crusades and it was brought here for safekeeping.

Below, the view of Oberburg from the walkway to the Matthias Kapelle.
On the right, a view of Oberburg from below, the steepness of the vine-covered slopes obvious.  While there is a trail that will take you up this slope, the best route is up along the south side of the hill, and then around the back.  The trail is easy to find, with signs initially pointing the way.

While the path appears well-traveled, the castle was deserted when I arrived.  The interior is in ruins, and allows one a perfect chance to examine the construction and architecture of a castle that is close to 1,000 years old.  The interior had plenty of archways, passages, and steps.  Portions of broken walls attest to the size of the interior buildings before they were destroyed. 

The view at the bottom right shows the Matthias Kapelle in the background.