What are the 'Hitler's Eyes' tunnels, and are they actually from WWII?

Yes — the 'Hitler's Eyes' tunnels are WWII German military observation posts carved into the limestone cliffs of the Šibenik Channel during the German occupation of Yugoslavia (1941–1945). The tunnels provided observation of ship movements through the channel and were positioned to give clear sightlines in both directions. The name 'Hitler's Eyes' (Hitlerove oči) is the local term that has stuck from the occupation period. The tunnels are a standard stop on the GYG kayak tour — paddling to them and viewing the channel from inside the cliff adds a very different layer of military history to the Venetian fortress context.

Is the kayak tour suitable for families with children?

The tour requires basic swimming ability and the capacity to sit in and paddle a sit-on-top kayak. Most tour operators recommend a minimum age of around 8–10 for children, and participation requires that all participants can swim. Sit-on-top kayaks are stable and suitable for beginners — the paddling distances are moderate and the channel water is generally calm in summer. Life vests are provided. Confirm age and ability requirements with the operator at the time of booking; the GYG listing carries the operator's current participation requirements.

UNESCO World Heritage

St. Nicholas Fortress

Tvrđava sv. Nikole

Croatia · Šibenik, Dalmatia, Croatia · Near Šibenik

Built 1540 · Venetian hexagonal naval fortress built on a rock at the entrance to the Šibenik Channel; designed by Giangirolamo Sanmicheli; massive stone casemates and artillery bastions designed to allow crossfire with the St. John and St. Michael fortresses on the mainland shore; inaccessible by foot, experienced by most visitors from the water

This page is part of an independent travel guide and is not affiliated with, endorsed by, or operated by St. Nicholas Fortress.

St. Nicholas Fortress in the Šibenik Channel, Croatia — the 16th-century Venetian hexagonal fortress on a rock at the entrance to Šibenik harbour, viewed from the water on a sea-kayak tour, with massive stone artillery casemates rising from the sea

Quick Facts

Hours: Daily Not publicly accessible by foot
Guided tour from: €65
Duration: Viewed from the water on a kayak tour (30–45 minutes paddling around the fortress)
Best time: May to September
Nearest city: Šibenik

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Šibenik: Sea Kayaking Tour to St. Nicholas Fortress

⭐ 4.9 (42)Top Rated·3 hours

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Highlights

✦One of the finest Venetian military fortresses in the Adriatic — St. Nicholas Fortress was designed in the 1540s to produce overlapping fields of artillery fire with the St. John and St. Michael fortresses on the mainland, forming a three-fortress defense-in-depth system at the entrance to the Šibenik Channel
✦UNESCO World Heritage Site — the Venetian defence works of Šibenik (St. Nicholas, St. John, St. Michael, and the Old Town) were jointly inscribed in 2017 as an exceptional example of Venetian Renaissance military architecture
✦Best experienced from the water — St. Nicholas sits on a rock in the Šibenik Channel and has no public access by foot; the GYG sea-kayak tour paddles past and around the fortress, giving views of the sea-level casemates and artillery bastions that no land-based visit can replicate
✦The GYG sea-kayak tour (t963522, from €65, 4.9★ / 42 reviews) includes the fortress paddle-past alongside a visit to the WWII 'Hitler's Eyes' lookout tunnel carved into the channel cliff and a swimming stop in the channel
✦The Šibenik Cathedral of St. James — a UNESCO World Heritage Site in its own right (2000), the 15th-century Gothic-Renaissance cathedral built entirely without mortar is a 10-minute walk from the kayak launch point

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St. Nicholas Fortress was built by the Venetian Republic starting in 1540 to guard the narrow entrance to the Šibenik Channel — the sea passage that led to Šibenik's harbour and the Krka River beyond. The design was produced by Giangirolamo Sanmicheli, one of the leading Venetian military architects of the period, and the result is a masterwork of Renaissance fortress planning: a hexagonal fortification with massive artillery casemates at the base and gun platforms above, positioned on a rock in the channel so that its guns could fire in coordination with the fortresses on the Šibenik shore, producing overlapping fields of fire that made the channel entrance almost impassable for any hostile fleet.

The fortress was built in response to direct Ottoman threat: the 16th century was the period of maximum Ottoman naval expansion in the Adriatic, and the Venetian Republic needed its Dalmatian harbour towns heavily protected. St. Nicholas was the seaward anchor of a four-fortress system that included St. John and St. Michael on the mainland and the city walls of Šibenik itself. The system was successful — Ottoman forces never breached the Šibenik channel. The entire Venetian fortification system was inscribed as a UNESCO World Heritage Site in 2017 for its exceptional quality as an example of Renaissance military engineering.

The fortress sits on its rock in the channel and is not publicly accessible by land. There is no ferry or regular boat service to the fortress island, and the site is not set up for walk-in visitors. The way most travelers experience it is from the water — and the GYG sea-kayak tour (t963522) is the standard way to do this. The tour launches from the Šibenik shoreline, paddles out to and around St. Nicholas Fortress, continues to a WWII 'Hitler's Eyes' observation tunnel carved into the channel cliff, and concludes with a swimming stop in the channel. Viewing St. Nicholas from the water, at the level of the sea-facing casemates, gives a scale and perspective on the fortress that no land-based view can provide.

History

The Venetian Republic began planning the fortification of the Šibenik Channel entrance in the early 16th century as Ottoman naval power expanded into the Adriatic. Construction of St. Nicholas Fortress began in 1540 under the design of Giangirolamo Sanmicheli; the fortress was substantially complete by 1549. The coordinated defensive system — St. Nicholas in the channel, St. John on the hilltop above the city, and St. Michael on the inner harbour — successfully deterred Ottoman naval attack throughout the period of Venetian rule. After Venetian control of Dalmatia ended in 1797 (following Napoleon's dissolution of the Republic of Venice), the fortress passed to French, Austrian, and eventually Yugoslav administration. WWII saw the channel cliffs used for military observation posts — the so-called 'Hitler's Eyes' tunnel visible on the GYG kayak tour is a German WWII installation. The UNESCO inscription of the Venetian fortification system of Šibenik in 2017 brought renewed international attention to the quality of the three-fortress ensemble.

How to Visit

Getting there: Šibenik is on the Dalmatian coast between Split (75 km south) and Zadar (85 km north), accessible by bus and car on the coastal highway. The GYG sea-kayak tour (t963522) launches from a point on the Šibenik channel shore and is the standard way to view St. Nicholas Fortress from the water. The fortress is not accessible by land.

Tickets: St. Nicholas Fortress itself has no walk-up ticket price — there is no public access. The GYG sea-kayak tour (t963522, from €65 per person, 4.9★ / 42 reviews) includes all equipment (kayak, paddle, life vest), guide, swimming stop, and the full tour itinerary — the fortress paddle-past, the 'Hitler's Eyes' WWII tunnel, and the swimming break. All tour costs are included in the €65/person price.

Practical tips: The kayak tour requires basic swimming ability and is suitable for beginners — no prior paddling experience is needed. Book at least a day in advance in summer; the tour operates in small groups and fills quickly in peak season (July–August). After the kayak tour, Šibenik's old town is worth 2–3 hours: the Cathedral of St. James (UNESCO, 2000), the city walls of St. Michael Fortress (walkable, views over the channel), and the waterfront promenade.

Combine with: [Kamerlengo Castle](/castles/croatia/kamerlengo-castle) (~25 km south in Trogir's UNESCO old town — the 15th-century Venetian fortress on the waterfront, accessible on a guided walk of Trogir's medieval centre) and [Barone Fortress](/castles/croatia/barone-fortress) (in Šibenik itself — the 17th-century Baroque fortress above the city, with a multimedia historical exhibition and views over the cathedral).

Frequently Asked Questions

St. Nicholas Fortress is one of the most architecturally significant fortresses in the Adriatic — a UNESCO-listed Venetian Renaissance masterwork — and it is the defining landmark at the entrance to Šibenik's harbour. Most travelers who visit Šibenik see it from the waterfront or from the ferry. The GYG sea-kayak tour is not a workaround for inaccessibility — it is genuinely the best way to experience the fortress, giving a water-level perspective on the casemates and artillery bastions that no land visit (if one were possible) could replicate. For anyone interested in Venetian military architecture, the kayak view is the appropriate way to understand how the fortress was designed to function.