Brunkebergsåsen was an esker that once reached over much of Stockholm's Norrmalm district.
It formed a considerable obstacle to traffic, effectively dividing Norrmalm into a western and an eastern part.
[1] Consequently, most of it has been dug away over the centuries to make room for the development of that district.
Conspicuous remnants of the esker can be seen in the vicinity of Johannes kyrka, at Observatorielunden, and Vanadislunden.
Essay, with several maps, on the city's development in Stockholm City Museum's publication CITY, Del I Byggnadsinventering 1974-75, pp 9–37 (Swedish) Media related to Category:Brunkeberg at Wikimedia Commons