Video report by ITV News Asia Correspondent Debi Edward
Donald Trump has become the first sitting US President to enter North Korea, after stepping into the territory from the Demilitarised Zone during a meeting with Kim Jong-un.
During talks, the two leaders also agreed to restart nuclear talks within weeks.
Mr Trump and the North Korean leader shared a history-making photo opportunity after meeting briefly and shaking hands across the border.
Speaking from the North side of the border, Mr Trump told those gathered: "It feels great."
The pair then walked back across the border into South Korea where they praised the friendship they have.
Mr Trump said he was "proud" to have stepped into North Korea.
Speaking through a translator, Mr Kim commended Mr Trump for crossing the demarcation line, which he called a "courageous and determined act" that "means that we want to bring an end to the unpleasant past".
In return, Mr Trump hailed the "great friendship" between the two men and the "progress" which had been made in relations between the two countries.
"A lot of really positive things are happening... tremendous positivity, really great things are happening in a lot of places," Mr Trump said.
"We met and we liked each other from day one, that was very important."
The US President also also said he would invite Mr Kim to visit the White House.
Kim reciprocated it would be an "honour" to invite Mr Trump to the North Korean capital of Pyongyang "at the right time".
Mr Trump’s brief crossing into North Korean territory marked the latest milestone in two years of roller-coaster diplomacy between the two nations.
Personal taunts of "little rocket man" and threats to destroy the other have been ushered out by on-again, off-again talks, professions of love and flowery letters.
Despite the meeting between the two leaders being scheduled to be little more than a handshake and pleasantries, they then held 50 minutes of talks where they agreed to restart nuclear talks within weeks, although Mr Trump stated "speed is not the object" and they would focus on "getting it right".
"The relationship that we have developed has meant so much to so many people," Mr Trump said.
"It's just an honour to be with you, and it was an honour that you asked me to step over that line and I was proud to step over the line...
"I want to thank you, it's been great."
The US President also took to Twitter to tell the world of the "honour".
Although there is an apparent willingness to restart talks, significant doubts remain about the future of the negotiations and the North’s willingness to give up its stockpile of nuclear weapons.
North Korea has yet to provide an accounting of its nuclear stockpile, let alone begin the process of dismantling its arsenal.
The US has said the North must submit to “complete, verifiable and irreversible denuclearisation” before sanctions are lifted.
The leaders of the technically warring nations were joined in the Freedom House conversation by Mr Trump's daughter and son-in-law, Ivanka Trump and Jared Kushner.
Will the visit mean North Korea becomes a step closer to becoming nuclear free? Debi Edwards explains
Until progress is made in any upcoming talks, US sanctions on North Korea will remain in place.
Yet the US President did leave open the possibility of scaling them back, saying that: "at some point during the negotiation, things can happen."
The meeting earlier this year is said to have entered difficulties, according to the White House, when Mr Kim was "unprepared" to commit to denuclearisation when pushed to do so.
In response, the US did not lift sanctions on North Korea which it said it would if an agreeable deal was reached.
Mr Trump paid his visit to the DMZ and North Korea during a visit to South Korea which had been planned to coincide with the recent G20 in Japan.
According to the 73-year-old, the meeting with Mr Kim had not been scheduled and only came about when he suggested it on Saturday.
Speaking as he prepared to meet with the North Korean leader, Mr Trump said: "Yesterday I had the idea: 'Maybe I'll call Chairman Kim and see if he wants to say hello'," Mr Trump told members of the US and South Korea's military inside the DMZ.
"So, we didn't give him much notice, but we respect each other, maybe even like each other, and he's agreed to meet."
Presidential visits to the DMZ are traditionally carefully guarded secrets for security reasons.
Ahead of the meeting, South Korean President Moon Jae-in, who accompanied Mr Trump inside the DMZ praised the two leaders for “being so brave” to hold the meeting and said: “I hope President Trump will go down in history as the president who achieves peace on Korean Peninsula.”
Ahead of the meeting, Mr Trump had said he looked forward to meeting with Mr Kim, but sought to tamp down expectations, predicting it would be “very short”.
“Virtually a handshake, but that’s OK. A handshake means a lot,” he said.
During his time in the DMZ Mr Trump also visited an observation post and greeted US and South Korean troops.
Peering into North Korea from atop Observation Post Ouellette, Mr Trump told reporters before meeting Mr Kim that there has been “tremendous” improvement since his first meeting with the North’s leader in Singapore last year.
Mr Trump claimed the situation used to be marked by “tremendous danger” but “after our first summit, all of the danger went away.”
Mr Trump took to Twitter on Saturday to announce that he had suggested a meeting with Mr Kim.
“If Chairman Kim of North Korea sees this, I would meet him at the Border/DMZ just to shake his hand and say Hello(?)!” he tweeted.
Meeting with Mr Trump at South Korea’s presidential Blue House on Sunday, Mr Moon said when he saw Trump’s invitation to Mr Kim, “I could really feel that the flower of peace was truly blossoming on the Korean peninsula.”
Every president since Ronald Reagan has visited the 1953 armistice line, except for George HW Bush, who visited when he was vice president.