The story comes from Switzerland but it has another version in Austria
In the canton of Bern, a cave near the city of Burgdorf, which is famous for its castle is called Drachenloch, in English – Dragon-cave. They say two giant dragons were found here long back before the castle was built.
According to the local legend, in the year 712, two brothers named Syntram and Beltram, whom others called Guntram and Waltram were the dukes of Lensburg. They came to this area to hunt and discovered the deserted forest on the top of the hills. In a cave there, lied a monstrous dragon which had desolated the entire area till far. It was probably starving as there was no other animal left in the forest. As soon as it noticed the humans, it jumped at them and instantly devoured Bertram, his younger brother, alive. Syntram however was able to defend himself. He charged at the dragon with indomitable courage. After a long fight, he finally defeated the wild creature. The giant’s big stomach was split – Beltram was still alive inside.
The two brothers now had a reason to immortalize their victory. They decided to build a castle here and constructed a chapel dedicated to Holy Margaretha on the spot where the dragon was killed. The story of their encounter with the dragon was inscribed on its wall.