The Stone Ioannovsky Ravelin was constructed between 1731 and 1740 according to the design of military engineer B. K. Minikh on the site of the first wooden-earth ravelin of the Peter and Paul Fortress, built at the eastern tip of Hare Island in 1704–1705. Casemate barracks were arranged within the thickness of the walls, and on the left facade were the Ioannovsky Gates, adjacent to which were guard rooms—cordegardias. On both sides of the ravelin are half-counterguards connected to it by flanks. A wide moat filled with water separated the ravelin from the Petrovskaya Curtain (filled in 1891). Today, the existence of the moat is recalled by partially preserved botardos—barrier dams with small towers—turels and fences—palisades, which separated the moat from the Neva River and the Kronverksky Strait. In 1787, according to the design of engineer R. R. Tomilov, the Neva facade of the southern half-counterguard of the Ioannovsky Ravelin was faced with granite slabs.
In 1894, the northern half-counterguard was rebuilt, where, according to the design of military engineer V. F. Asmus, a one-story building was constructed for the untouchable reserve of the Izhora Reserve Battalion. In the 1930s, this building housed the first domestic design bureau for the development of rocket engines—the Gas Dynamics Laboratory (GDL) (since 1973—the Museum of Cosmonautics and Rocket Technology named after V. P. Glushko).
In 1909, according to the design of engineer S. A. Chistogradov, a residential building for officers of the Life Guards Rifle Regiment was erected in the southern part of the ravelin. Today, the restaurant "Austeria" is located here.
In April-May 2008, repair work was carried out in the fortress. In the Ioannovsky Ravelin, this affected the spitz and the drawbridge.
Sources:
https://ru.wikipedia.org/wiki/Иоанновский_равелин_Петропавловской_крепости
https://www.spbmuseum.ru/themuseum/museum_complex/peterpaul_fortress/objects_fortress/ioanovski_ravelin.php
