Nyiragongo volcano, in the western branch of the East African Rift system, is among the most active volcanoes on Earth, and one of the most hazardous African volcanoes. Its flank eruptions in 1977 and 2002 triggered disasters, affecting a population that already suffers from years of socio-political instability. The main eruptive activity of Nyiragongo corresponds to the presence of a persistent lava lake in its summit crater. This lava lake can be seen as an interesting opportunity to monitor the activity of the volcano, as some of its level variations translate volume and pressure changes in the upper volcanic plumbing system. The lava lake could consequently provide precursory signals associated with an upcoming flank eruption. In order to study the lava lake activity of Nyiragongo, we combined different remote sensing techniques, based on synthetic-aperture radar (SAR) satellite imagery, and photographs acquired during helicopter flights, drone surveys and ground-based campaigns. These techniques are complementary and provide an overview of the different types of lava lake level variations observed at Nyiragongo. Mono- and stereo-photogrammetry are used to measure minute to day-scale lava lake level variations and surface movements, through ground-based time-lapse image acquisitions in the Nyiragongo crater. Structure-from-Motion photogrammetry with images acquired during helicopter flights and drone surveys allows monitoring major changes in the Nyiragongo crater, by measuring volume changes and ground deformation associated with the lava lake activity. Photogrammetric ground deformation measurements correlate with those performed by SAR interferometry. Finally, long-term lava lake level monitoring and trend change detection are obtained using shadow measurements on SAR amplitude images coming from ENVISAT, RADARSAT-2, TanDEM-X, Cosmo-SkyMed and SENTINEL-1 satellites.