Some of the main ideas of the fractal city theory are briefly reviewed, and their applicability is tested for the medium and small-size Romanian urban settlements. The universality of Zipf law for cities and towns distribution is proved once again and a stochastic master equation is proposed in order to explain the empirical distribution. The urban structure of Bucharest is investigated as an example of medium-size city formed by merging some independent poles of growth. The Central Places Theory is found to be in disagreement with the real urban structure. Instead, the diffusion-limited aggregation and self-organized criticality mechanisms are investigated by means of some numerical simulations and are found to fit better the urban perimeter growth.