Arnarker Cave - Mystery with bonus Mystery Cache

It takes about an hour to drive from Reykjavik to the lava tube cave named Arnarker in Leitahraun lava field.
From the road there's a short path to the cave's entrance, but the cave is a hollow pit that reaches down about 16 metres vertically.
The ceiling of the cave probably broke a few thousand years ago. It is amazing it actually broke considering the depth of the cave itself. The cave is usually called "Kerid", but it's older name is Arnarker or Eagle's Basin, although no eagles have nested in this lava field in recorded history.
The pit is the only entrance and there is a sturdy ladder down into the cave, which measures over XXX metres in length.
The cave is also quite spacious, both in width and in height, although the cave's northern tunnel is more or less collapsed. The breakdown deposits cover the whole floor, except for the first 100 metres, which are mostly covered by a coating of ice.
During the late season of winter, the ice constructs amazing and beautiful formations of ice castles, some of these are over 3 metres high.

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To get the coordinates of the final cache, please answer the question:

What is the lenght of Arnarker Cave in meters? (rounded to the full hundred)

(in checker please write 3-digital number only, e.g. 100, 200, 300...)