The church in Ostaszewo was built in the first half of the 14th century. It was burnt in 1945 by the retreating German army and has been in ruins since then.
The church was built on a rectangular plan. It was an orientated, one-nave building with a tower from the west. The porch adjoined the southern wall. The eastern wall was distinguished by a beautiful, blend-pinnacle gable. The brick base of the tower was built on a rectangular plan with the upper wooden part. The whole was reinforced with numerous buttresses.
The ruin of the church in Ostaszew is currently an object with full-sized perimeter walls and a fragment of the eastern gable. It is secured, but not shared inside for sightseeing.