Welcome to Fortress Larne, not Inver Park (home of Larne FC) but Olderfleet Castle. Sure it's not the biggest in the world but it's got an interesting story to tell.
The original towerhouse was possibly built by the Scoto-Irish Bissett family of Glenarm around 1250, although these remains are actually thought to be those of Curran Castle, a towerhouse built in the sixteenth century. On a 1610 map it was called Coraine Castle.
In 1315 Edward Bruce landed here with his 6000 strong army en route to conquer Ireland, with a welcome from the Bissetts. Queen Elizabeth I considered the castle of such strategic importance that it was seized for the crown and Sir Moyses Hill appointed its governor in 1569. In 1597 the castle was claimed by the MacDonnells and in 1598 it was dismantled.
The present castle was probably built about 1612. In 1621 it was granted to Sir Arthur Chichester and remained in that family until leased to William Agnew in 1823. James Chaine purchased the lease in 1865. In 1938 it was taken into State Care.
There are several handy parking spots nearby and access to the castle site itself is free.
The cache should be a relatively easy find if you start feeling around. It's not a very busy spot but watch out for muggles who can approach from several directions.