The Field of Mars is a large square in the centre of Saint Petersburg. Over its long history it has been alternately a meadow, park, pleasure garden, military parade ground, revolutionary pantheon and public meeting place.
The space now covered by the Field of Mars was initially an open area of swampy land between the developments around the Admiralty, and the imperial residence in the Summer Garden. It was drained by the digging of canals in the first half of the eighteenth century, and initially served as parkland, hosting a tavern, post office and the royal menagerie. Popular with the nobility, several leading figures of Petrine society established their town houses around the space in the mid eighteenth century.
Wikipedia https://en.wikipedia.org/wiki/Field_of_Mars_(Saint_Petersburg)
Address Санкт-Петербург 191186, Russia
Coordinates 59°56'36.834" N 30°19'53.781" E