Cast iron is very durable, almost five times stronger than granite. It is possible to create a lightweight constructions. Bulky curved arches of stone bridges of the 18th century are gone. There were graceful arches made of steel (Cast iron). The first bridge, where the metal were used, was the bridge at the intersection of Nevsky Prospekt and Embankment (1806). Before the revolution it was called the Police, or the Greens, and later became the People. Petersburg architect V. Hastie had used the idea of engineer Robert Fulton.

The span was covered in a gentle arch of steel, which were collected from the cast-iron blocks. They resemble the shape of inverted boxes. The walls were made of blocks openings through which the bolts were passed, which cemented blocks, boxes, one with another. Such a construction of the bridge with steel deemed very successful. Thus, the project became a model – the world's first standard metal bridge project. Under this project by the end of the first decade of the 19th century metal, which were cast iron units, procured for a series of new bridges over the Sink. In 1814, the first was built at Red Bridge Sinks and crossing the street Gorokhovaya (now Dzerzhinsky street). Only after 140 years, its cast-iron arch has been replaced by modern steel structures.

Those bridges over the Sink, which were built by the first half of the 19th century – indeed Masterpieces of Russian architecture, although they all have the same design (cast-iron arches are composed of blocks, boxes). In all of this architecturally designed bridge is almost always original. On bridges installed fine metal grid and lights, which now strike us with his jeweler's precision manufacturing. For example, the 1st Engineers installed the bridge lights, floor lamps in the form of beams and rails peak were decorated with images of crossed swords and shields with mythical Gorgon Medusa's head.