Welcome to Hadrian's Wall
When completed, the mammoth structure ran across the island's narrow neck, from the Solway Firth in the west almost to the mouth of the Tyne in the east. Every Roman mile (0.95 miles) there was a gateway guarded by a small fort (milecastle) and between each milecastle were two observation turrets. Milecastles are numbered right across the country, starting with Milecastle 0 at Wallsend – where you can visit the wall's last stronghold, Segedunum – and ending with Milecastle 80 at Bowness-on-Solway.
A series of forts was developed as bases some distance south (and may predate the wall), and 16 lie astride it.