Schauenberg Castle, Castle ruin on the Schauenberg hill near Turbenthal, Switzerland

Schauenberg is a castle ruin near Elgg situated on elevated terrain that commands views across the surrounding region. The stone remains show the basic layout of a medieval fortification with distinct areas still visible to those who explore the site.

Around 1200 a wooden noble's residence stood on the west side above a cellar cut into the rock; around 1250 it was rebuilt as a massive stone keep, with a neck ditch cut across the hilltop. The castle is first documented in 1260 as castro Schowenberc. In 1344, after Beringer von Hohenlandenberg broke the peace, Austrian officials with citizens of Winterthur and Zurich destroyed it; few finds suggest it was already abandoned.

The name Schauenberg appears in writing in 1260 as castro Schowenberc, while Rudolf von Schauenberg is documented in 1242. From 1622 Zurich kept a beacon chain here against the threat of the Thirty Years' War; signals from the hill could be seen as far as the Uetliberg, the Lägern and Hohenklingen. The site is still a destination for walks above Winterthur.

The ruins sit on the 892 m Schauenberg above Elgg and Turbenthal; the canton of Zurich owns the upper hill and leases the alp. Two marked routes cross it: No. 69 Züri Oberland-Höhenweg (stage 1, Winterthur–Girenbad) and No. 872 Tüfelschilen–Schauenberg. The summit opens views to the Alpstein, the pre-Alps, the Alps and the Black Forest.

The upper part of the hill, with the ruin and a triangulation point at 894 m, belongs to the canton of Zurich, which leases the whole alp. The ruin is a class B Swiss cultural property of regional significance. The 1976–1979 cantonal excavations also uncovered the remains of the early modern beacon.