Sentences of a paragraph are given below in jumbled order. Arrange the sentences in the right order to form a meaningful and coherent paragraph.

A. The guide warned us that we would have to climb 937 steps to reach the top of the ancient tower.

B. We occasionally passed small windows cut into the wall.

C. At first we started counting the steps ourselves, but we soon lost patience.

D. As these gave little light, we felt as if we were going round and round a dark tunnel.