COUNTRY
ID, NAME, {Other Data}

REGION
ID, CID, NAME, {Other Data}

CITY
ID, RID, NAME, {Other Data}

COUNTRY <-----> REGION <------> CITY
        1     n        1     n

from City c where c.rid in (select r.id from Region r where r.cid = {country id}

public class Country {
   private Long ID;
   private Set<Region> regions;
   public  Long getID() {
      return this.ID;
   }
   public  void setID(Long id) {
      this.ID = id;
   }
   public  Set<Region> getRegions() {
      return this.regions;
   }
   public  void setRegions(Set<Region> regions) {
      this.regions = regions;
   }
   public Set<City> getCities() {
      Set<City> cities = new HashSet<City>();
      for (Iterator iter = regions.iterator(); iter.hasNext();) {
         Region element = (Region) iter.next();
         cities.addAll(element.getCities());
      }
      return cities;
   }
}

public class Region {
   private Long ID;
   private Country country;
   private Set<City> cities;
   
   public Set<City> getCities() {
      return this.cities;
   }
   public void setCities(Set<City> cities) {
      this.cities = cities;
   }
   public Country getCountry() {
      return this.country;
   }
   public void setCountry(Country country) {
      this.country = country;
   }
   public Long getID() {
      return this.ID;
   }
   public void setID(Long id) {
      this.ID = id;
   }
}

public Country loadCitiesForCountry(Long countryID) {
   Session session = openSession();
   Criteria loadQuery = session.createCriteria(Country.class);
   loadQuery.add(Restrictions.idEq(id));
   loadQuery.setFetchMode("regions", FetchMode.JOIN);
   loadQuery.setFetchMode("regions.cities", FetchMode.JOIN);
      
   Country c = (Country) loadQuery.uniqueResult();
   session.close();
   return c;
}