I visited Crespi D'Adda on the 20th of December this year. I had been thinking about this day trip for quite a while and, now that I have finished my exams, I took a day for myself to explore this little town just over an hour from where I live. I got off at the wrong bus stop and walked half an hour to reach it (a time it would have taken me even at the right stop). First advice: don't visit in December like I did because you're going to miss much of the experience! Most of insude spaces (like the hydroelectric central or the Crespi house) are closed from December to February and are only available through guided tours from March to November. Still, I had quite the good time. Since the day was sunny, I walked around most of the day and got to see some of the key sites of the town (although only from the outside) like the church, the main buildings of the factory, the Crespi family house, the graveyard (with an absurdly big mausoleum for the Crespi family) and of course the single-family houses. 

In a day you should manage to see just about everything in the town, even better if you go by car and don't have the time costraints I had. A few practical tips: I suggest stopping by the Crespi Cultura association in the eastern part of the town which can give you a map of the city with the main sights and routes. Since the town is so tiny, there's not much choice when it comes to eating; your options are either a bar which may or may not sell sandwiches, a bakery which closes at 1:30 or, if you don't have a problem with spending some more money, one of the three restaurants in town. I personally went at the Dopolavoro which has quite a bit of history itself and is an overall nice restaurant and pizzeria, despite costing more than I thought. I also suggest heading up the hill to the belvedere, which provides a beautiful sight of the town, and stopping by the hydroelectric central of Trezzo D'Adda, which may be considered part of the site and is built in the same architectonic style, if you have time to spare. 

Overall, the town is certainly an experience; I'm not sure about its OUV but, being from Northern Italy myself and having seen a lot of Italy, I can say I have never seen a similar place and the vibe alone is worth it imo. Granted, keep in mind that there's not much to do and that at the end of the day it is still a fully inhabited town, so be mindful of not disturbing the few inhabitants!

Photos by me!