FFair Rhaglan is the largest annual SCA event in Insulae Draconis. It takes its name from Castell Rhaglan (Raglan Castle) in Wales where it is held. It currently runs for two weekends and the intervening week, and is typically scheduled early in August, often opposite Pennsic.
There are a number of traditional battles which take advantage of the castle location - gate battles through actual gates, bridge battles on actual bridges, and so forth. The location makes the use of hay bales to create terrain superfluous.
CADW's Castell Rhaglan site - http://cadw.gov.wales/splash?orig=/default.asp?id=6