Captain America and Mr. Fantastic have made it to the rooftop by using the Fantastivator. Doctor Octopus is trying to escape across the rooftops hoping to leave behind the heroes since there are large gaps in between the buildings. Both heroes will have to work together to cross the rooftops to stop Doctor Octopus.
Save game if you have not already done so.
Mr. Fantastic needs to glide across the rooftops. Places were he needs to glide are marked by blue squares with two white arrows pointing the direction. Get a good running start and try to glide to the other rooftop. Be sure to angle upwards to get over the railing. If you are having difficulty gliding in this area, use the ladder to climb back up to the upper level and glide over from there.
The rooftop has a small greenhouse on it that needs to be destroyed. This will begin the counter for the canister for this stage. You will need to destroy a total of five greenhouses to collect the canister. On the corner of the building is an antenna. Destroy the antenna to build a rope to the building that Captain America is still on for later use.
See the complete article at GameSkinny.com on Taking Back the Baxter Building.