//...
public class Place {
	
	public Set<Place> reachablePlaces(){
		Set<Place> discovered = new HashSet<Place>();
		Queue<Place> worklist = new LinkedList<Place>();
		discovered.add(this);
		worklist.add(this);
		while(!worklist.isEmpty()){
			Place p = worklist.remove();
			for(Place n : p.neighbors()){
				if(!discovered.contains(n)){
					discovered.add(n);
					worklist.add(n);
				}
			}
		}
		return discovered;
	}
    //...	
}