which city in europe has exactly 9,80665 of acceleration due to gravity?

Answer 1

I would say Paris as the origin of SIU, but it is not.

Answer 2

As you may know, the actual acceleration due to gravity varies across the surface of the Earth. Gravimetry is the measurement of gravitational fields, and includes the study of these variations. 9.80665 m/s^2 is considered the standard acceleration due to gravity on the surface of the Earth, and is approximately the acceleration at a latitude of 45.5 degrees (or 45 degrees and 30 minutes), north or south or the equator. Milan is located at north latitude 45°28', which is very close to what we're looking for, and I don't see any other cities in Europe at a close latitude, so I think that must be the one.

Edward's answer is quite good, and probably correct. However, it exposes a flaw in the question, if so. The question asks which city in Europe has this acceleration. But Paris does not, because 9.80665 is the acceleration due to gravity if Paris were at sea level, which it is not. In fact, most of Europe at this latitude is occupied by the Alps, so there is probably no predictable location where acceleration due to gravity assumes this value.