Attached Link: http://www.geocities.com/Paris/Rue/4235/DLSkies.htm

Danny Eilat's site has lots of skies in .sky format. As for creating an arch or tunnel - create a lattice - then go into the Terrain Editor - Click New - draw your arch or tunnel click on the check. Then select the arch, click on the A box for attributes - rotate on the x axis -90 and you're done. Hope this helps, Jade