This activity is part of the Cycle Planning. Each cycle is a month, and starts by detailing the high-level plan created in the Preparation for the upcoming month. This section shouldn't take more than 3 days.
You need to get everyone together for a couple of hours to a full day, for a team-building activity (e.g. going hiking, to a picnic, etc). Be sure that people are socializing with their peers in other companies (if there are external companies) rather than their coworkers in the same company.
By conducting this activity properly, the professional communications among experts will be more effective in the future, which benefits the project significantly.