The Heidelberg Project is a hidden gem in Detroit. Well, it's not exactly hidden, but it's definitely off the beaten path. A few weeks back, my friend had a visitor from Greece/Germany who wanted to see it. I was more than happy to take him. I have been a handful of times, but it had been years since my last visit. It's always nice to rediscover something in your own city.
You can read all about what The Heidelberg Project is here and if you ever visit Detroit, make sure you pay it a visit. There's nothing else quite like it.