The stairwell is located a few steps away from the Kasanas' home.
Celebrations for a family in Greater Noida near Delhi turned into despair within moments as a one-year-old died on his birthday after falling from the 12th floor.
The incident took place at the Casa Greens 1 housing society of Greater Noida on Monday.
To celebrate his son Riwan's first birthday, Satyendra Kasana and his family members were decorating their home and relatives and guests had also arrived.
Little Riwan was playing in the common area outside their flat's main door when he fell through the grills of the stairwell and dropped 12 floors down. He was taken to hospital, where he was declared dead.
The child had slipped out of the apartment unnoticed, the family says.
A video of the building shows the door to Kasanas' home and then moves a few steps away to the stairwell through which Riwan fell.
In the video, the stairwell can be seen with an iron handrail and horizontal rows of iron bars running parallel to the handrail.