NOTE: This ice arch has collapsed but I'll keep it in here to serve as a reminder of all the unique and sometimes temporary gems Iceland has to offer at each moment.
It was located on the south coast, nestled in the Kötlujökull glacier which is a part of the mighty Mýrdalsjökull glacier. It was formed by melting water carving through the ice and offered a unique peek into Iceland's volcanic history with ash from Katla eruptions dating back centuries. Every now and then, formations like these appear so feel free to message me and ask if I know of anything similar at this moment.
QUICK NOTES:
What it was: An ice cave in Katla Glacier on the south coast, collapsed now.
Message me: For current information about something similar.
Best season: Any season but could be hard to get to during winter.
Best time of day: Any time of day.
Nice to know: I highly recommended doing this with a guide.