The dominating geological features in the Eurasia Basin are two sub-parallel ridges, the Lomonosov and Gakkel ridges. Both systems are more than 1800 km long and their origin is closly related to the Cenozoic history of the basin. The Gakkel Ridge represents an active mid-ocean ridge.During the early rift/drift phase the Lomonosov Ridge was formed and represents today the northern rim the Eurasia Basin. Before the ridge was attached to the Barents and Siberian shelves. The seafloor spreading processes along the young Gakkel Ridge finally separated the Lomonosov Ridge from the Eurasian continent. One of the astonishing observations is that the rift process left behind a 1800 km long and only 200 km wide ridge. This is a first order observation. New seismic data indicate that the ridge is much more broken at upper crustal levels than previously thought. Below a Cenozoic layer with a thickness of 500 to 1200 m, older basement is visible in the data, which was affected by tectonic processes, most likely during the rift phase. Bathymetric and seismic data close to the Siberian margin show that the ridge is much wider than the bathymetry might suggest. Some smaller elongated ridges in the Makarov Basin are likely to structurally belong to the Lomonosov Ridge. This might indicate that closer to the Laptew Sea margin a more complex and long-living rift process was active than in the center of the basin.