Mikaelshulen

Mikaelshulen is a well-visited cave on the shorelines of lake Norsjø near the town of Skien. Skien is about 2.5 hour drive southwest from Oslo. The cave has acted as a catholic church, dating back to 1300s, and was also an important place of pilgrimage. It isn't large -- 25 meters by my measurements -- but is definitely awe-inspiring with its location on a cliff, overseeing a lake, and sun shining directly into the cave. Today it is a popular hiking destination.

According to references, "Church in Mikjálsbergi" was listed in year 13987 in a bishop's land ownership book as an owner of land in the area. The cave was named after Archangel Michael in Catholic times, some time before the Reformation 1536-1537. From the Reformation until 1843, the church was a refuge for remaining Catholics. Practicing Catholic faith was a serious crime after Reformation. 

A description from 1643 calls the cave "Templum Mirabile" (wondrous temple). 

Above the cave, at the top of a mountain there is also an ancient burial ground site. I didn't go see the burial ground, but read somewhere that the site hasn't been visible for a long time.

There are many St. Michael's churches in Norway, some of them in caves as the Archangel was often depicted fighting serpents or dragons.

But back to Mikaelshulen. This cave was formed when weaker rock weathered away, also helped by sea waves and ice when the cave was at sea level in the post ice age period. The cave may also have seen modifications or enlargements by humans; there aren't any obvious structures but of course additional rock might have been chipped away. In today's state the cave also has some graffit.

The cave is reachable on foot, or by boat, and is a popular hiking and tourist attraction. Boats can arrive on the pier built by the lakefront, close to the cave.

The cave is in the middle of a massive cliff ending right at the lake, today at an altitude of 30 meters above the lake. There is a well-prepared trail to the cave, but it does involve first some stairs. And then just before the cave you'll need to do some climbing on a steep rock face, helped though by metal handrails:

I scanned the cave with my iPhone's lidar sensor, and then processed it to get a plan view and some vertical cuts of the cave shape. The 3D model can be downloaded here, or rotated on your browser screen here. The full PDF map is accessible here. Below are some sample photos of the model and the map, however.

According to my model, the cave is roughly 25 meters from the drip line to the end. Other sources list the length usually at 20 meters, though. Not sure if my iPhone lidar is inaccurate.

Other articles about this include Wikipedia, Velma Aho's blog post, ut.no article, cultural memory search site entry, skiensatlas page, showcaves.com entry, visitnorway page, and visittelemark page.

There's a parking lot to get to the cave at . There's a well-prepared trail, one way length is about 1.7 km. The trail vertical gain is around 100 meters. Here's the trail map:

More pictures of the cave:

Climbing:

View from the top of the trail to the lakes:

Signs on the road:

This article has also been published at Planetcaver.net here. Read the full Planetskier series at planetskier.net, urban exploration stories from theurbanexplorer.net, and other underground stories from planetcaver.net, or all blog articles from Blogspot. Photos and text (c) 2026 by Jari Arkko. All rights reserved. The drone picture showing the cliff from above the lake is from ut.no article by Skien-turlag.