In a city like Edinburgh there's always something new to discover, and many residents don't even know about the huge tunnel running under the city.
The Innocent Railway tunnel sits beneath Holyrood Park, and is entered in a quiet residential close behind St Leonard's police station. Once you're in, the end of the tunnel seems a fair distance away - and is in fact an impressive 517 metres long, reports the Scottish Daily Express.
Built in the 1820s, the tunnel was used to transport coal between Dalkeith and Edinburgh with horse-drawn carriages. This is where the name Innocent Railway comes from, as steam engines were seen as dangerous.
