Naumachia, or naumachia, was a gladiatorial naval battle in Ancient Rome, and later came to denote any spectacle imitating a naval fight. It was considered a particularly luxurious spectacle. Structures for such events, including artificial water bodies with stands for spectators, were also called naumachias. Few know that the Russian Empire also had its own 'naval theater.' The water complex with decorations for naval reconstructions was designed and built by the Russian architect Nikolai Lvov. During construction on the banks of the Kolpanka River in the late 18th century, Lvov noticed a spring with clear water near the under-construction 'Cascade with a Lock.' He decided to create a miniature version of the 'Naumachia' in Syracuse, an ancient theater for naval battles. Lvov gave his Naumachia the appearance of ancient ruins, striving to recreate the look of past naval theaters. The water body was framed with granite, leading to a stone staircase with fragments of marble columns reminiscent of ancient Rome.

Over half a century, the structure deteriorated due to weather conditions. In 1854, it was repaired: the pool, terraces, and steps were restored. Subsequently, no further work was carried out here. The columns collapsed, and the cladding cracked. Today, the Naumachia is partially covered with turf and hidden by tall grass.

Additionally, Gatchina housed a mysterious underground passage known as the Grotto 'Echo,' built in the 18th century. The exit to the lake shore is framed by an arch resembling a cave made of wild tuff. The grotto got its name for its acoustic properties: sounds are repeated inside the underground passage. The echo is particularly well heard if the listener is at some distance from the basement (near the second pair of lanterns). There is a legend that in October 1917, the chairman of the overthrown Provisional Government, Kerensky, used this passage to escape from the Gatchina Palace, fleeing from sailors led by Dybenko. However, Alexander Fyodorovich himself does not confirm this in his memoirs.