As early as the 1950s, the amateur theater group in Sonnberg called it "curtain up". © Franz Amon 12. May 2022 A/NOE: Topotheque Hollabrunn-Sonnberg online Curtain up for the third Topotheque of Hollabrunn: after Hollabrunn-City and Hollabrunn-Breitenwaida, the Topotheque of Hollabrunn-Sonnberg has now also gone online. Sonnberg, incorporated into the municipality of Hollabrunn in 1972, proudly looks back on a long history. There is nothing left of the former castle, but the newly built castle from its stones, completed in 1596, is still one of the sights of Sonnberg today. But it is better to look at it from the outside, because inside it has been a prison since 1955! Before the castle was sold to the administration of justice, it belonged to Archduke Anton von Habsburg-Lothringen, an enthusiastic amateur pilot. But the Topotheque Sonnberg has much more to offer than just the castle, as you can see for yourself by taking a tour of the various photos and documents!