The Poppenberg is a tree-covered hill east of Ilfeld in the Harz mountains of Germany, with a height of 601 metres. Since 1897, there has been a steel lattice observation tower on the summit. The tower was built by the Nordhausen branch of the Harz Club and was named after Otto, Prince of Stolberg-Wernigerode. In good weather, it has an extensive view over the South Harz, the Goldene Aue and the Kyffhäuser.