Cole still didn't believe. Despite the fact that Castiel hadn't exactly made his status as an angel unknown, Cas supposed he couldn't hold it against him. Cole seemed used to people being able to will themselves from one place to another or augmented strength. Even though it was not within God's Divine Plan, Cas knew all to well that with God absent in his world, it stood to reason that He could be absent elsewhere.
"I could show you," he offered. "I am...permitted to perform a small miracle. However, what I am about to show you is between you and myself. We do not show our wings to just anyone. In fact...there are only two humans in existence who have ever witnessed this. You will be the third."
It wasn't that Castiel didn't trust Cole. His wings were on a plane of existence separate from that of his vessel and even if the other man somehow managed to find them or touch them, there was a more than stable chance that they would burn Cole alive, but after all that had happened to him in the past two years, Cas was wary of allowing anyone near his wings.
Carefully, he stepped over to the edge of the building, using the one next door as a backdrop. Its windows were heavily tinted and mostly dark. They would do. He focused his Grace, calling the black cloud overhead. Thunder rumbled and lightning cracked just enough to leave a lingering flash long enough on Castiel himself. Long enough that the shadow of two massive black wings spreading behind him was cast.