Tandil is the main city of the homonymous partido (department), located in Argentina, in the southeast of Buenos Aires Province, just north-northwest of Tandilia hills.

The climatological data in the table below is from the period 1991–2020: It is widely believed that the name of the city comes from the Mapuche words tan ("falling"), and lil ("rock").

It is probably a reference to the Piedra Movediza ("Moving Stone"), a large boulder which stood seemingly miraculously balanced on the edge of a rocky foothill.

[6] In order to demonstrate the slight movements of the boulder, it was common practice to place bottles under its base to watch them shatter.

Tandil was designated a city (although by modern standards it was a large town) in 1895 and became a popular tourist destination attracting people from Buenos Aires and other parts of Argentina.

This was the way the locals would prove to visitors that the rock, in fact, moved, since the movement was too subtle to be detected by the naked eye.