The problem of positioning cameras for optimal monitoring of a given surface, while given a budget, is quite evidently hard. Moreover, it is very difficult to collect information that could reduce the span of admissible solutions and therefore downsize the problem itself. In this paper, as referred to a specific case in a critical infrastructure, the harbour of the Ventotene Island in southern Italy, how the above mentioned problem can be solved in an effective way by employing a Genetic algorithm. The approach is also generalised in order to solve similar problems.