User blog comment:Calbeius or Urukgoth/A Calbeius Original: The Explanation of Evil in the Fourth Age/@comment-27718380-20160103183156

1.How did Dol Guldur survive? Lets see. According to a Wikia Contributor, Dol Guldur was attacked and took over by the Elves of Lorien during the War of the Ring.

2.The Dol Guldur Orcs actually escaped through a series of caves. They rode on spiders through lots of webby caves. They traveled through the caves until they could make it into Mirkwood Corrupted.

3.Lorien and the Wood Elves were to clear out the infestation of Spiders through Mirkwood. One of the problems was that Dol Guldur was actually repopulating the spiders. The other problem was that Lorien and the Wood Elves didnt know where they were being repopulated. They could tell Dol Guldur was repopulating the Mirkwood Spiders because everyday when were to clear out the spiders, they always came back.

4.Dol Guldur knew that as long as its inhabitants stayed alive, then the more chance Dol Guldur can repopulate and kick out Lorien and possibly the Wood Elves. The Orcs of Dol Guldur repopulated around Mirkwood Corrupted. Lorien couldnt find the Spider Nests, which led to the captured Dol Guldur City to be overrun by Mirkwood Spiders. Lorien had to retreat back to their home of malorn trees. Dol Guldur reclaimed their capitol of Dol Guldur. They kept the spider population at a balanced rate.

Now, I've split this up so it's easier to answer.

1. Lothlorien did attack them, yes. But Dol Guldur was almost nothing after the two attacks against Lothlorien had failed.

2. Show me evidence of the existence of these. Right now, you're just arguing for something that has no purpose. Amon Lanc would've seemed impregnable a few years hence, so it wouldn't be worth making such tunnels, and the manpower and time required was nowhere near what they had to make them.

3. Nay, it is stated that Galadriel and Celeborn did this, so we can assume that it was Galadriel's last usage of her 'magic' after tearing down the walls of Dol Guldur.

4. The spiders had no affiliation to Dol Guldur, so if you imagine a city infested with horses to us it would be annoying as hell, but we can't control them all. Also, considering my other arguments they most likely died, and Mirkwood was renamed to Eryn Lasgalen when East Lorien was founded by Celeborn.