By building a worker, your population decreases by 1
By building a settler, your population decreases by 2
This means, in order to "Raze" your own city, you need to continue to decrease the population.
Set all of your tiles inside your city to entertainers, or taxmen, or scientiest .. what ever you want. Hence no food, so your population will decrease.
So once ur population get's small enough, the last worker/settler will cause ur city to disapear.