error: session can not resolved

In the code below I'm getting the message: session can not resolved which prevents you from running the code snippet.

package controler;

import org.hibernate.Criteria;
import org.hibernate.Session;
import org.hibernate.criterion.Restrictions;

import antlr.collections.List;
import model.negocio.entidade.agenda.Atividade;

public class Teste {

    public static void main(String[] args) {

        Criteria cr = session.createCriteria(Atividade.class);
        cr.add(Restrictions.eq("tipoAtiviade", "status_id"));
        List results = cr.list();


    }
}