"These are tank drops, they're rigged with C-4 (explosive)".
That was the first sign we were getting close to the Korean border.
We'd driven under a structure you could mistake for a bridge, pillars on either side of the road.
"In the event North Korea were to invade and head south, we can blow these tank drops, the two concrete pillars will fall onto the road and block the paths of any oncoming tanks."
Add that to the barbed wire fences, the regular guard houses (every third one or so is manned), the multiple checkpoints.
My cameraman Richard and I had started the day in Seoul.
It was quiet.
The lunar New Year meant the hustle and bustle was at a minimum. But otherwise it was still exactly as you imagine a big city to be.
People drinking, eating, socialising, shopping. Taxi drivers keen to point out the City Hall, the ancient Gyeongbokgung Palace.
No hint that just a hour and a half drive's north is the world's most dangerous border.
We were going up with some New Zealand Defence Force personnel, to do a story on their roles at the DMZ. Those roles vary - communications, monitoring the border crossing, training soldiers and operations management - all aimed at ensuring the 65-year-old armistice isn't breached.
It was eventful.
There were the aforementioned tank drops. At one point a lieutenant pointed out where a land mine had claimed the legs of two South Korea soldiers in 2015 (North Korea is suspected of planting it, but it hasn't been confirmed).
At another Richard had to jump out of the car to sort out a camera issue.
"Don't go off the road" he was warned. There are millions of land mines in this area. Leaving the tarseal is a risk you don't want to take.
When we arrived in the DMZ filing limitations were put on us. They don't want the North Koreans to be able to get a look at certain South Korean defences, or the locations of their bases.
We were shown where representatives can meet and negotiate, and came within 10 metres of the exceptionally ordinary plain white stakes that marked the demarcation line between the countries.
We were shown how those stationed at the UN Command post - including a New Zealander - contacted the North.
It's an eyebrow-raising system of calling, getting no answer, going to the demarcation line and shouting the message, getting no answer, calling again, getting no answer.
Eventually the north sends down a cameraman to the border, and films the message as its read out.
Here you have to be careful - you don't want to end up able to be used on a North Korean propaganda video.
It was eerie. And tense. It's always tense.
Because it was a public holiday, there weren't as many guards present as normal, no tourists (it's a huge attraction, the Southern side of the DMZ gets around 125,000 tourists per year), and propaganda wasn't blaring from the North's speakers like it often is.
Just a group of Kiwis and the odd American, chatting about Kim Jong Un, political tensions, home… 10 metres away from a reclusive country run by a tyrannical regime, which is responsible for heightening nuclear tensions around the world.
We talked about the North Korean soldier who'd defected not far from where we were standing. He was shot multiple times as he made his escape, within metres of a hut labelled the 'Peace House'.
The defector survived.
He now has to be integrated into a society vastly different from the one he risked death to get away from.
One that can seem so far removed, even when it's scarily close.