Zlenice-Hláska, Gothic castle ruin in Senohraby, Czech Republic.

Zlenice-Hláska is a castle ruin on a promontory above the right bank of the Sázava River, where the Mnichovka stream joins it. Its two-part layout, with a bailey and a core of the block type, survives mainly as the torso of a residential tower linked to the gate tower.

Founded around 1300, Zlenice was first documented in 1318 through Oldřich of Zlenice. In 1377 Charles IV granted it as a fief to Ondřej of Dubá, and in 1463–1465 it was besieged and destroyed; crossbow and hook-gun projectiles found at the outer gate confirm the assault.

The castle's name is recalled in the local nickname Hláska, used for the tower remnant above the Sázava. The site is a protected cultural monument of the Czech Republic, and since 1996 the Sdružení pro ochranu kulturního dědictví – Zlenice has cared for the ruin and begun its conservation.

The ruin stands on a promontory above the right bank of the Sázava, reached by a footpath on the slope; a wooden viewing platform was completed at the core gate in 2011 and the path around the castle was reinforced. The terrain is uneven, so wear sturdy shoes.

The local name Hláska comes from the castle's preserved tower remnant, a name that has been used in the area for centuries. This tower remains one of the most recognizable features that visitors see while exploring the ruins.