What is the name of the cavity that the heart is found in?

The heart is in the thoracic cavity in a part called the mediastinum. It is protected by the pericardium, a membranous sac that surround the heart. The mediastinum is that space in the thoracic cavity between the lungs that contains the heart. It also contains the aorta, esophagus, trachea and thymus.
The pleural cavity is the space in the chest between the lungs.