This is basically what it looked like (after the exploding started). It was a dome structure that was open at the top. At this point the rest of the dome has pretty much collapsed completely.
https://steamuserimages-a.akamaihd.net/ugc/1820017355105711133/D94CA311121C2DF4909B5803042EB42CD4BCE2D6/?imw=5000&imh=5000&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false