The Toba caldera is located in north Sumatra, Indonesia. It is part of the volcanic arc associated with the subduction of the Australian Plate beneath the Southeast-Asian Plate. The subduction zone, and the Sumatra Fault, a right lateral strike-slip fault which marks the plate boundary, are seismically active. In order to investigate the volcano-related seismic activity and image the volcano related structures (i.e. a potential magma chamber) using ambient noise techniques a dense seismic network was installed around Lake Toba between May and October 2008. The network, deployed within a German-Indonesian cooperation, comprised 42 continuously recording seismic stations equipped with three-component, short-period seismic sensors with 1 Hz natural frequency. The GPS-synchronised data loggers recorded at 100 samples per second for the experiment's time span of 6 months. During this time period local and regional seismicity was recorded. The array of stations covers an area of approx. 150 by 200 km with inter-station distances of about 20 km. The station distribution is quite irregular due to the difficult environmental conditions. Data from all stations are freely available from the GFZ seismological data archive.