Fort Kronshlot is a stone fortress sitting on an artificial island in the middle of the water, and it has been there, in one form or another, since 1704. Peter the Great ordered it built to guard the shallow channel to the new city of Saint Petersburg, and the first version was a wooden tower on piles driven into the seabed and filled with stone. The name comes from the German for crown castle. The current structure is mostly of the nineteenth century, a long oval of brick and granite with gun casemates facing the water.
Kronshlot sits two kilometres from the town of Kronstadt, which is just far enough to feel remote and just close enough to see. Together with the other forts of Kotlin, it was part of a system that made the capital almost impregnable from the sea. The system was tested during the Crimean War, when British and French ships approached and prudently turned away, and again during the world wars. Today the fort is mostly empty, and the waters around it are favoured by fishermen and the occasional rowing club.
The ride to Kronstadt along the Dam is an experience of its own. For about twenty kilometres you cross the gulf on a causeway with water on both sides, passing the sluice gates and the great ship passages that keep the city safe from storm surges. The road is straight and smooth, the wind can be fierce, and the horizon is huge. In clear weather you can see Kronstadt's gold dome from far away, and when mist rolls in the whole scene turns to pearl.
Autumn storms can push the sea high against the embankments, and in winter the ice can stretch to the horizon. Spring and summer are easiest, with warm sun, long evenings and light traffic outside rush hours. Observe the speed limits and look out for cameras.
Kronstadt itself has fuel, food and shops, and the harbour area has cafés where you can sit with a view of the water and the forts. A bag with a warm layer is a good idea even in summer, since the gulf breeze can be chilly.