Whangārei is the only city in Northland, and you'll pass through on a road trip between Auckland and the Bay of Islands.
I'm going to be honest with you, if you asked most Kiwis, they'd tell you that while Whangārei has some beautiful things to see, it’s not the kind of place you’d plan an entire trip around.
However, that doesn't mean it's not worth visiting. I love Whangārei Heads, where you'll find one of my favourite trails in Northland, the Te Whara Track! If you find yourself in the centre of Whangārei, go and have lunch/brunch by the Town Basin, and you cannot leave without visiting Whangārei Falls!
There's a lot to see near(ish) Whangārei too. If you're driving north from Auckland to the Bay of Islands, detour through the Tutukaka Coast. This is a beautiful drive, full of white sandy coves that you could easily spend days hopping between. If you're heading south, stop at Piroa Falls just after Whangārei and then detour to Waipu - a cute little town with lots of shops, a brewery and Little 'Lato (one of my fav ice creams!!)