Kotlin Island lies in the Gulf of Finland, at the entrance to the Neva, and its job for three centuries has been to guard St Petersburg from the sea. Peter the Great founded the naval base of Kronstadt here in 1704, and the island, long and narrow, was ringed with forts, batteries and artificial islands. The northern batteries, of which No. 4 is one, belong to that long chain, built in the eighteenth and nineteenth centuries as the guns grew bigger and the ships more dangerous. They are low, grass-covered earthworks and brick casemates facing the water, and on grey days the place has a lonely, military feel. The sea is shallow here and often frozen in winter.
Kronstadt has a bigger place in history than its size would suggest. In 1921 its sailors, once the heroes of the revolution, rebelled against the Bolshevik government, and the uprising was crushed in a few days. The town's naval cathedral, a big domed building with a restored interior, stands in the centre, and a harbour of old dry docks and brick warehouses has been made into a quiet, interesting walk. For decades the island was closed to outsiders, and travel there was only opened in the 1990s.
A flood-protection barrier, completed in 2011, carries a road across the water from the mainland to Kotlin, and this is how most people arrive. The road is flat and fast, with the grey water on both sides and the horizon a thin line, and the wind is the main thing a rider will notice. On the island, the roads are straight and the surface is mixed. Summer evenings are very long this far north, and the white nights give a soft pearl light until after midnight. Winters are bitterly cold.
Access to some military areas can be restricted, and entry rules for visitors can change, so check what is allowed before you go. Kronstadt, a few kilometres away, has fuel and shops, and Gorskaya and Aleksandrovskaya are smaller. Midsummer is the best time for the light, and a day trip from Saint Petersburg is easy.