Whether at 1,000, 3,000, or 30,000 feet - you still need to be 1000ft above the highest obstacle within 5nm.
'Cos it hurts when you make a "CFIT"
Technically the "1000 feet above the highest obstacle within 5nm" doesn't apply if you are below 3000 feet and visual with the ground - though hacking along 500 feet above the trees at 245 knots in 300m vis fog defo is in the legal but dumb category!