Kostrzyn Fortress Museum

What's left of the original river fortress (pretty much nothing but a few cobble stones) can be walked through within 10 - 15 minutes. The gates on either end and part of the bastions have been renovated. In summer, having a lunch break on top of the Bastion Brandenburgia can be enjoyable, with views of the Odra. The interior (entrance ticket required) can be visited between April and October.

Right before/after the border bridge, there are old fenced-off barrack buildings on the left and right side of Detlefsenstraße, which can make for an eerie scene on a gloomy autumn/winter day – the road sees little use. Built by the Nazis, the Russians took over and used the facilities after 1945, and left them to rot in the early 90s after Germany's reunification.