Seaplane Harbour

A symbiosis of engineering and marine history

The Seaplane Harbour in Tallinn is one of the city’s most remarkable architectural landmarks, combining early 20th-century engineering innovation with 21st-century museum design. Its story spans more than a century: from its origins as part of Imperial Russia’s naval defence system, through turbulent decades of war and Soviet occupation, to its reinvention as Estonia’s most visited maritime museum. For us at KOKO Architects, working with this building meant not only conserving a unique structure but also giving it a new, public life.

Creation 1916-1917 and use before II WW

The Seaplane Hangars were built in 1916–1917 as part of the defensive complex protecting the Gulf of Finland. At the time, Estonia was still within the Russian Empire, and the complex was designed to host seaplanes that could patrol the coastline and secure naval dominance in the region.

The hangars were revolutionary for their time. The immense concrete domes—spanning 36 meters without internal supports—were among the first large-scale examples of thin-shell concrete construction in the world. Their design was both bold and pragmatic: three interlinked halls created vast open space where aircraft could be moved and serviced freely.

After Estonia declared independence in 1918, the hangars served the new Estonian Air Force. During the interwar years, the facility became a hub of military aviation, reflecting the young republic’s strategic need to protect its long coastline.

Soviet time

The Second World War disrupted this continuity. The Soviet Union occupied Estonia in 1940, followed by German forces in 1941, and then the Soviets again from 1944 onwards. During these years, the seaplane hangars were adapted for different military uses, including storage, workshops, and naval operations.

Although the building remained structurally impressive, decades of neglect, heavy use, and lack of proper maintenance left it scarred. Concrete surfaces deteriorated, leaks developed in the massive shells, and the spatial clarity of the hangars was gradually obscured by partitions and makeshift alterations. By the late Soviet period, the structure was decaying, and its original architectural brilliance was almost invisible behind layers of utilitarian adaptation.

Reconstrution and turning into a maritime museum

After Estonia regained independence in 1991, the question arose: what should be done with this unique but endangered building? Its historical value was obvious—it represented both world-class engineering and a vivid part of Estonia’s military heritage. At the same time, it was clear that without a new function, the hangars would continue to deteriorate.

The idea emerged to transform the Seaplane Harbour into a branch of the Estonian Maritime Museum. The ambition was bold: to conserve the extraordinary concrete domes and, at the same time, to create a museum capable of housing large vessels, including the 1930s submarine Lembit, one of Estonia’s national treasures. This vision required not just technical expertise but also a new architectural approach that could bring together conservation, exhibition, and public space.

KOKO design

When we at KOKO Architects were invited to design the transformation, we saw it as both a challenge and a privilege. Our guiding principle was to respect the raw power of the original hangars while carefully weaving new layers of architecture that would serve today’s visitors.

We began with the building itself. The three domes were cleaned, repaired, and revealed in their full clarity. Instead of covering imperfections, we allowed traces of history to remain visible, letting the patina of the concrete tell its own story. This decision anchored the museum in authenticity.

Inside, we introduced a suspended exhibition landscape. Steel walkways and platforms float within the hangars, allowing visitors to experience the vast scale of the space while engaging with ships, aircraft, and artifacts from different vantage points. At the centre, the submarine Lembit rests as a dramatic focal point, with smaller vessels and exhibits arranged around it. The walkways spiral and cross at different heights, creating a dynamic and theatrical journey through maritime history.