The biggest challenge in the construction of Marbruk was bringing the stone into Valenwood. The Wood Elves have few quarries, and the forest in these parts is so overgrown, the ground so fertile, that it's difficult to find quality deposits. In addition, Queen Ayrenn expressly commanded that we disturb as little of Valenwood to build the city as possible.
Interestingly, Wood Elves from outside Valenwood and from the bigger settlements, such as Woodhearth, have objected more strenuously to Marbruk's construction than the local Wood Elves, who are mostly fascinated by the stone constructions rising up among them. If I had to guess, I'd say that the symbolic importance of Valenwood is greater for those who don't live there than for those who do. It's as if these more "civilized" Wood Elves fear they've already compromised their culture in some way, so they feel obligated to protest the construction.
Queen Ayrenn has assured both parties of Wood Elves that Marbruk is necessary to the defense of the Wood Elf way of life, especially against the Ebonheart Pact, and so far this assurance seems to have prevented any serious interference with our work, although there has been the occasional incident of tools going missing or stone being carved into perverse shapes overnight.