The research of urban anthropogenic habitats has recently gained big emphasis. We started the systematic mapping of the urban flora and habitats of Budapest, Hungary in 2018. Our main goal was to create a comparable study on the anthropogenic urban habitats of the inhabited areas. The territorial units were street sections, where we recorded the presence of vascular plants separately in each ecologically habitat. Based on the experience gathered during the field survey, we distinguished 18 ecologically anthropogenic urban habitats. We recorded 647 spontaneously plant species in more than 27,000 survey units. Our survey evinced the spontaneous occurrence of 193 alien plant species in Budapest. Our knowledge about the distribution of 81 of them is insufficient, while 10 are new introductions in Hungary. 53.9% of the aliens are cultivated frequently in Hungary. Our research suggests that there is a need for systematic mapping of urban habitats because these areas are centers of introduction and spreading of aliens, while may serve as refuges for native species at the same time. The most species-rich habitats are attached to roads, they bear the most adventive species as well. The corridor role of roads is also supported by our research.