This is the coolest photo I ever saw!!! Is this is a lava tube??? I really like your ND filter use... Can you write the settings you used??? It looks like you are at the same place for a wile now... Or you just posting pictures from the same trip??? Is this is the same place with waterfalls??? This is really cool!!!!
This is the place called "Subway", located in Zion National park.
The tube was created by water "stream". (In same way as Antelope canyon). Yes, this picture from the same trip, but from a different place. Taken Nov 3, 2011. The image still has all the EXIF info, you can open it on your computer to see all the info.