Title: Engines of God
Published: Voyager, 1996
Purchased: Waterstones, Cambridge, 2004-02-26, £6.99
Humanity has conquered the stars. They have FTL, but they've only found two candidates for possible terraforming, one occupied by another race already. So Quraqua is the only option. The problem is, there are archaeological remains there that will be destroyed by the terraforming, so it's going to be a race to get the evidence before terraforming starts.
(Oh, and strange artefacts have been found on various worlds.)
In the end, the dig ends in tragedy due to bloodymindedness. But it has put the archaeologists on a hunt for more clues that lead to other worlds, where it seems that huge destruction seems to come at about 8000 year intervals. What, or why, is the great search that then takes place, with much danger and some Big Dumb Objects.
In the end, it seems that there really is something that does not like a wall.
Good hard SF, though the characters are a little forgettable for me.