Ioannovsky Ravelin, Ravelin of the Peter and Paul Fortress in Saint Petersburg, Russia

The Ioannovsky Ravelin is the eastern ravelin of the Peter and Paul Fortress, a triangular outwork shielding the Gosudarev and Menshikov bastions, the Petrovsky Curtain and the Petrovsky Gate. Built in stone in 1731–1740 to Minikh's design, its thick walls hold casemate barracks, and the left face contains the Ioannovsky Gate with adjoining guardhouses. Half-counterguards linked by flanks stand on both sides.

A first wooden-and-earth ravelin was built at the eastern tip of Zayachy Island in 1704–1705. The stone Ioannovsky Ravelin replaced it between 1731 and 1740, designed by military engineer B. K. Minikh, and was named after Tsar Ivan V, Peter I's elder brother. Its water-filled moat separating it from the Petrovsky Curtain was filled in 1891 during construction of the permanent Trinity Bridge.

The ravelin is named after Tsar Ivan V, Peter the Great's elder brother and father of Empress Anna Ioannovna. Its left face holds the Ioannovsky Gate, flanked by guardhouse rooms. Since 1973 the building of the former Gas Dynamics Laboratory, founded in the 1930s as the country's first rocket-engine design bureau, has housed the V. P. Glushko Museum of Cosmonautics and Rocket Technology.

The ravelin stands at the eastern tip of Zayachy Island, reached from the fortress centre through the Ioannovsky Gate in its left face, where guard rooms once adjoined. The water moat that separated it from the Petrovsky Curtain was filled in 1891, so the ground is now level; fragments of the botardo dams with their small turrets and palisades survive along the Neva and Kronverksky Strait. The Gorkovskaya metro station is the nearest.

The moat separating the ravelin from the Petrovsky Curtain was filled in 1891, and the granite-faced Neyva facade of the southern half-counterguard dates from 1787. In 1930s the north half-counterguard building housed the Gas Dynamics Laboratory, the country's first rocket-engine design bureau, now the Museum of Cosmonautics and Rocket Technology.