There are a number of us around these days and there are assloads of sites to explore, even in Gangnam. Most arent on UER but people do meet up mostly on weekends.
I just crossed the river today to visit Bamgol Village which is an old neighbourhood in Dongjak-gu with only a few remaining houses. Weeks before that area is done.
https://www.instagram.com/p/BTOUn-wBnxi/ My advice is just go out on walks in your neighbourhood and look for signs of inactivity. Try buildings you work and live and others nearby for rooftops. Good exercise and in a perfect world, everybody scouts.