While the square dates back to the foundation of the city in the 12th century, most of its buildings were constructed after the Great Fire of 1795 in Neoclassical style.

Surprisingly, its name is not a reference to adjoining Nytorv but to the slightly younger Amagertorv, Copenhagen's other major market in early times.

[1] Copenhagen's first town hall, of which practically nothing is known, was built on the east side of the square but later destroyed during Hanseatic capture and pillaging of the city in 1368.

Towards the end of the 16th century, King Frederick II provided for the construction of a water tube from Lake Emdrup.

Six kilometres long, it was made from carved out tree trunks, and with an altitude difference of 9 metres the water pressure was high enough to erect Copenhagen's first fountain at Gammeltorv.

[2] When Kongens Nytorv—King Christian V's grand new place royale—was established in 1670 and the area of the Copenhagen fortified was doubled, Gammeltorv lost its status as the focal square of the city.

To commemorate the tercentenary of the House of Oldenburg's accent to the Danish throne, the City Magistrate erected an octagonal memorial temple in the square in 1749.

From the same date all trade in pork meat was stopped at Gammeltorv while the poultry ladies were allowed to continue their activities by the Caritas Well until 1 April 1917.

The building at the corner with Nygade (Gammel Torv 2/Nygade 6), on the other side of the square, is from 1898 and was designed by Aage Langeland-Mathiesen in a style inspired by Renaissance architecture.

A modern proof of Gammeltorv's historic role as the centre of the city is that house numbers in Copenhagen proceed from the end of the street which is located closest to the square.