The apartment water cut-off valve is located In the laundry, behind a panel that requires a key to open. This key should have been provided to you when you bought the apartment.Inside the panel there is a cut-off valve for the cold water and a second cut-off valve for the hot water.
In addition, there are seporate cut-off valuves for the hot & cold water for the washing machine found under the lanundary sink and a cut-off value for the kitchen sink found under kitchen sink.