Rostock's Steintor (city wall) has two faces. The side that met outsiders is plain, with a coat of arms and a row of loopholes. The message: don't try it. The side that faced the city is a different building altogether.

There, two lions hold the coats of arms of the duke, the city and the Hanse, the trading league Rostock belonged to. Below them, a Latin inscription wishes the city harmony and well-being. The gate dates from 1575. The wall around the town once had 22 gates, and four survive.

VoiceMap's self-guided audio tour of Rostock follows the longest surviving stretch of that wall, 450 metres of it, and explains how fire, war and a growing city left only fragments.