# Understen lighthouse

> lighthouse in Norrtälje Municipality, Baltic coast, Sweden

**Wikidata**: [Q33196656](https://www.wikidata.org/wiki/Q33196656)  
**Source**: https://4ort.xyz/entity/understen-lighthouse


## References

1. [Bebyggelseregistret](http://kulturarvsdata.se/raa/bbrb/21420000029894)
2. [Fyrwiki](https://fyr.org/wiki/index.php/Understen)
3. Swedish list of lights. 1978
4. notice to mariners. 1992
5. [NGA List of Lights, Radio Aids and Fog Signals. 2021](https://msi.nga.mil/api/publications/download?key=16694312/SFH00000/NIMA_LOL/Pub116/Pub116bk.pdf)
6. Admiralty List of Lights and Fog Signals