get brass key go south and west from grand exchange in varrock but stay on the varrock side of the river.
there is a house you use key enter and go down for hill
giants. they drop big bones limpwurt roots a few magic
runes, and are very good experience and money although, there are known to be dozens of people for alot less giants, so you may have to world hop to find a quiet place.
also, inside barbarian village the stronghold of security has many creature of a variety of levels to train on..level 1 has minotaurs, a renowned dropper of many iron arrows. level 2 has 24 zombies and 28 flesh crawlers, the latter regarded as an extremely efficient monster to kill even for higher levels.