I had this happen to me once.  I was building inside a 'Wildzone' and was close to a stone wall.  I knew I could change the terrain by raising & lowering the land, but when I tried, I was able to get the wall to disappear but I still could not build or move there.

If you can, I think your best chance is to try and 'snake' your way around one of the obstacles - that is, if you can't raise & lower the land.

Here's what I do; I created a 'Henchman' called 'Surveyer.'  The Surveyer has 2 main jobs.  First, he builds roads (as he levels-up, have him take 'path of the Governor').  Second, he raises & lowers land (must be 'Earth Mage').  So, after you create your Surveyor, get him enough experience to become a governor who can build roads.  As he levels-up, increase his 'Earth' skills until he becomes an Earth Mage.     Here are the stats for my Surveyor Henchman...

SURVEYOR

[Weapon]: Upgradeable Bow,  [Armor]: Leather everything (except shield),  [Equipment]: Horse, Amulet of Haste, Braided Belt,     [Traits]: Potential, Earth Adept, Precision.

When you're in a battle, just leave him in the background and use him as an extra bowman.  He shouldn't be any trouble. 

Be sure you give him a horse.  A useful technique for getting past another faction's outpost is to simply build a road through it.  With a horse (4 moves) your Surveyor should be able to build half of the road (and get back) in one turn, and finish the road on the next turn.  My armies can then ride past another faction's outposts and I never hear a word of complaint.