You can unblock from the app:
- browse to the community in question by using the search function
- tap the menu on the top right
- click the block button again (it will say it blocked the community)
- refresh the page
Community will be unblocked.
I don’t think there’s a list of blocked communities, so you have to know which community it was.
Translation according to Google translate:
“I found in the garden what looks like an old Christmas decoration from the early 1800s.”