The misuse of high-power electrical appliances such as air conditioners in both commercial and residential buildings has contributed to the inefficient use of energy resources. To face this scenario, smart buildings focus on minimizing energy consumption while improving the experience and productivity of users in these environments. Aiming at optimizing the use of air conditioners towards energy efficiency, this work presents Smart Place, an Internet of Things (IoT)-based ambient management system for automatically controlling those equipments. In this system, sensors and video cameras collect data regarding temperature, humidity, and presence of people in monitored spaces. These data are parameters for performing interventions on air conditioners in order to avoid keeping them turned on when the environment is not being used. The system also provides a Web interface for managing devices and monitored environments as well as it is integrated to the FIWARE platform as underlying middleware. This paper describes Smart Place, its architecture, and its operation at the Federal University of Rio Grande do Norte (UFRN), Natal, Brazil. The paper also discusses the benefits resulted from the automatic intervention performed by Smart Place, which has been able to save 61.8% in energy consumption compared to the traditional manual control in a set of classrooms.