The east side of the Kremlin triangle, lying adjacent to Red Square and situated between the rivers Moskva and the now-underground Neglinnaya River was deemed the most vulnerable side of the Kremlin to attack, since it was neither protected by the rivers, nor any other natural barriers, as the other sides were. Therefore, the Kremlin wall was built to its highest height on this side, and furthermore, the Italian architects involved in the building of these fortifications convinced Ivan the Great to clear the area outside of the walls in order to create a field for fire shooting. The relevant decrees were issued in 1493 and 1495. They called for the demolition of all the buildings within 110 sazhens (234 metres) of the wall.
In 1508–1516, the Italian architect Aloisio the New arranged for the construction of a moat in front of the eastern wall, which would connect the Moskva and Neglinnaya and be filled in with water from Neglinnaya. This moat, known as the Alevizov moat and having a length of 541 meters, width of 36 meters, and a depth of 9.5–13 m was lined with limestone and, in 1533, fenced on both sides with low, 4-meter thick cogged brick walls. Three square gates existed on this side of the wall, which in the 17th century, were known as: Konstantino-Eleninsky, Spassky, Nikolsky (owing their names to the icons of Constantine and Helen, the Savior and St. Nicholas which hung over them). The last two are directly opposite the Red Square, while the Konstantino-Elenensky gate was located behind Saint Basil's Cathedral. In the early 19th century, the Arch of Konstantino-Elenensky gate was paved with bricks, but the Spassky Gate was the main front gate of the Kremlin and used for royal entrances. From this gate, wooden and (following the 17th century improvements) stone bridges stretched across the moat. Books were sold on this bridge and stone platforms were built nearby for guns – "raskats". The Tsar Cannon was located on the platform of the Lobnoye mesto.
The square was called Veliky Torg (Great market) or simply Torg (Market), then Troitskaya by the name of the small Troitskaya (Trinity) Church, burnt down in the great fire during the Tatar invasion in 1571. After that, the square held the name Pozhar, which means "burnt". It was not until 1661–62, when it was first mentioned by its contemporary Krasnaya – "Red" name.
Red Square was the landing stage and trade center for Moscow. Ivan the Great decreed that trade should only be conducted from person to person, but in time, these rules were relaxed and permanent market buildings began appearing on the square. After a fire in 1547, Ivan the Terrible reorganized the lines of wooden shops on the eastern side into market lines. The streets Ilyinka and Varvarka were divided into the Upper lines (now GUM department store), Middle lines and Bottom lines, although Bottom Lines were already in Zaryadye).
After a few years, the Cathedral of Intercession of the Virgin, commonly known as Saint Basil's Cathedral, was built on the moat. This was the first building which gave the square its present-day characteristic silhouette (pyramidal roofs had not yet been built on the Kremlin towers). In 1595, the wooden market lines were replaced with stone. By that time, a brick platform for the proclamation of the tsar's edicts, known as Lobnoye Mesto, had also been constructed.
St. Basil'sRed Square was considered a sacred place. Various festive processions were held there, and during Palm Sunday the famous "procession on a donkey" was arranged, in which the patriarch, sitting on a donkey, accompanied by the tsar and the people went out of Saint Basil's Cathedral in the Kremlin.
During the expulsion of Poles from Moscow in 1612, Prince Dmitry Pozharsky entered the Kremlin through the square. In memory of this event, he built the Kazan Cathedral – in honor of the Kazan Icon of the Mother of God, followed his army in a campaign.
Zemsky prikazAt the same time (1624–1625), Spasskaya tower received contemporary tent roofs. This was done on the proposal and the draught of Englishman Christopher Galloway, who was summoned to design the new tower's clock (clock watch it there with the 1585) and suggested the arrangement of the tent roof over the clock. In the mid-century a gilded double-headed eagle was set on top of the tower. After this, the square became known as Krasevaya ("beautiful").
In the late 17th century (1679-1680) the square was cleared of all wooden structures. Then all Kremlin towers received tent roofs, except Nikolskaya. One tent was even erected on the wall above Red Square (the so-called Tsarskaya Tower, intended so that the tsar could watch from this spot the various ceremonies in the square). Tent roofs were also constructed at Voskrerensky (Iberian) gates, arranged in the wall of Kitai-gorod. These were the fortified gates at Voskresensky Bridge over the River Neglinnaya.
In 1697 and 1699, gates were built on both sides of Voskresensky onto large stone buildings: the Mint and Zemsky prikaz (department in charge of urban and police matters). Zemsky prikaz, then, was known as the Main Pharmacy (on-site new Historical Museum). The building of Zemsky prikaz in 1755 was organised by the first Russian University. At the same time in the Alevizov moat, where there was no water, a state Pharmacy's garden (for the growing of medicinal plants) was arranged. (wikipedia)