PHOTOS: North Korean leader Kim Jong Un arrives in Vietnam ahead of second nuclear summit with Trump

North Korean leader Kim Jong Un arrived in Dong Dang, Vietnam, at the border of China, on Tuesday.

As Business Insider's Alexandra Ma reported, Kim took a three-and-a-half day ride on an armored train to get to Vietnam.

Source: Business Insider

Kim Jong Un's sister, Kim Yo Jong, also traveled to Vietnam.

Kim Yo Jong has become "an important aide" to her brother. She serves as the vice department director of the Workers' Party's Central Committee.

Source: Reuters

From Dong Dang, Kim traveled to Hanoi.

Vietnam is a significant location for both North Korea and the United States.

North Korea provided both "material and personnel" to Vietnam during the Vietnam War against the United States, The New York Times reported, and there are gravestones in Vietnam (though their remains were repatriated) for North Korean pilots killed during the war.

For the US, Vietnam was the site of a long and ultimately failed war that ended with North Vietnam defeating the US backed south in 1975. Since 1995, the two countries have worked to normalize relations (and become healthy trade partners), which The Times noted could be a model for North Korea.

South Korea also normalized relations with Vietnam in 1992.

Sources: Council on Foreign Relations, New York Times

Kim and Trump are scheduled to meet for a second summit this week.

Trump has been tweeting ahead of the summit.

"Heading over to Vietnam for my meeting with Kim Jong Un," the president said, on February 25, local time. "Looking forward to a very productive Summit!"

The US Secretary State Mike Pompeo arrived on Tuesday.

The two leaders' first summit was in Singapore in June of 2018.

During their first meeting Trump and Kim laid out an agreement between the two countries:

1. The United States and the DPRK commit to establish new US-DPRK relations in accordance with the desire of the peoples of the two countries for peace and prosperity.
2. The United States and the DPRK will join their efforts to build a lasting and stable peace regime on the Korean Peninsula.
3. Reaffirming the April 27, 2018 Panmunjom Declaration, the DPRK commits to work toward complete denuclearization of the Korean Peninsula.
4. The United States and the DPRK commit to recovering POW/MIA remains, including the immediate repatriation of those already identified.

Source: CNBC

The two leaders hope to expand on their initial agreement.

And the world is watching.

Spectators — not just in Hanoi where they lined up to watch Kim's motorcade — are waiting to see if progress can be made between the two countries.