Το Σιδηρόκαστρο στο βιβλίο A HANDBOOK OF BULGARIA , 1920
A HANDBOOK OF BULGARIA Compiled by the Geographical Section of the Naval Intelligence Division^ Naval Staffs Admiralty An alternative road continues in a WSW. direction down the Oseno valley till it reaches its confluence with the Struma opposite Simitlii at mile 5. From this point there is a track up the 1. bank of the Struma joining the main Demir Hisar-Juma'-i-Bala road at the bridge 3 miles N. of Simitlii (see Route 26 at mile 74i). ROUTE 26 SERES—DEMIR HISAR—JUMA'-I-BALA, 83i miles This is one of the principal strategical routes, providing a line of entrance into Bulgaria via the Struma valley from the Salonica-Dedeagach railway at Demir Hisar. The light railway from Juma'-i-Bala was reported (Jan. 1917) to have been constructed as far as Rupel. From Seres to Demir Hisar is a good chaussee (according to report of March 1916) through open cultivated country. The soil is of hard clay and stony, providing good going in all weathers. From Demir Hisar to Juma'-i