(Among the Breslaver Hasidim, it has been a custom for more than 200 years to visit the grave of Rebbe Nachman, who taught in Breslav but passed away and is buried in the town of Uman. The Breslaver have been a small group. For many years, the Uman gathering attracted a few hundred people. In the last 20 years or so, it has become a gathering that includes a far wider cross-section of the Jewish people, and attracts — from what I’ve read — in the 10’s of thousands. 
The essay below appeared on the website cited, but without the name of a specific author. 
It conveys the natural intensity of Rosh Ha-Shanah and Yom Kippur, enlarged by the meaning of the particular place in which the gathering is occurring, and its resonance not only with Rebbe Nachman’s teachings but with his promised personal help for each person who journeys to Uman.)

Uman[1] There is no way to fully explain in words the magic of Uman Rosh Hashana. The emotions felt there are ones that need to be experienced to be understood. When asked to describe what it’s like, you’ll most likely get short explanations like “incredible,” “spiritually uplift-ing,” “unity,” “emotional,” “connected” … in most cases, you’ll probably just get a glazed over expression with a “You just gotta go, then you’ll understand.”

Over 200 years ago Rebbe Nachman brought forth a new wisdom; one in which each person can establish a deep and real connection with the creator of all things, Hashem. The Teachings he brought are literally endless in depth, covering every aspect of the Torah. But with all that he brought, he himself said of himself “ “Kol inyan sheli hu Rosh Hashanah!” – “My whole essence is Rosh Hashanah.”

There are many extreme statements that Rebbe Nachman said about himself in his life, but this one is by far the most extreme.

Rabbi Nachman explained that through Rosh Hashana he has the ability to help change and fix people at the very root of their soul. He said that there were certain individuals who he himself couldn’t effect a (spiritual) rectification [tikkun] for the entire year; however on Rosh Hashanah he was able to help even these people get their rectification.

What is the secret behind this?

Rebbe Nachman told [us] that Hashem blessed him with a special relationship with Rosh Hashanah as he said, “Hashem, blessed-be-He, granted me this as a gift that I know what Rosh Hashanah is.”

Rosh Hashana is the holy day of judgment for all the world, which can be a very intense and even frightening concept for many of us. It’s a time that we are taught to look back on our year and our life. To come face to face with what we have done. Did we strengthen our relationships with our fellow man and God? Did we do things to jeopardize it? How have we behaved? Spoken? There is so much room in our year for deep spiritual growth, but also for mistakes and falling. How can we make sure that on the day of judgment [“On Rosh Ha-Shanah the judgement is written; on Yom Kippur it is inscribed] we are really prepared?

If we truly contemplate the intensity of the day it’s hard to know where we stand at all!

This is one of the reasons thousands flock to the tzaddik each year. Rebbe Nachman is the only righteous tzaddik who said of himself that he knows all the 24 courtrooms in shamayim [Heaven] and can sweeten every din [judgement; “sentence”] in all these 24 judgment halls.

He didn’t say this because he was bragging; like a good doctor who knows what he is capable of healing and speaks about it in order to help as many as will come to him, so, too, the Rebbe is telling us to come to him so he can use all the spiritual influence he has to sweeten our lives!

Rebbe Nachman said “Whoever comes to me [in] Uman [on] Rosh Hashana, should be happy all the year.”

And maybe that’s why people are walking around [in Uman] on the most intense Jewish day of the year, with smiles on their faces. They feel the sweetness there without needing to be reminded.

Don’t be mistaken, the tzion (grave) is crowded with all kinds of people crying, shouting, pouring out their hearts, reading psalms. Being in Uman for Rosh Hashana is super intense. It’s a roller coaster of emotions. But at the same time people are walking around with smiles on their faces, like someone has just taken 100 heavy bricks off their hearts.

It’s probably the biggest unity of Am Yisrael [the people of Israel] you can find today. Jews of all backgrounds from all different countries; laughing, eating, dancing together. American, French, Israeli, German…. All colors of clothing and kippot, hats, and no head coverings at all; dancing, praying, drinking coffee and eating cookies together. There is a deep feeling of love and brotherhood towards every one you pass, weather you know them personally or not.

It’s hard to truly explain what is happening there in words.
The only thing that can be said is:
Go and experience it for yourself! [2]

(In Hasidut, the “tzaddik” is one — usually a man but there was one female tzaddik — who has brought their own relationship with God to a supremely advanced level, and through whom the individual hasid becomes “attached” to God. The followers of a tzaddik call him their “rebbe.” Each rebbe could be centered in a specific town. Thus, there have been the Lubavitcher Rebbe, the Kotzker Rebbe, the Premislaner Rebbe, etc. 
Yet, even within that Hasidic paradigm, Rebbe Nachman was unique in promising to continue his spiritual relationship with his hasidim after he had passed away. As a result, unlike every other Hasidic group, the Breslaver hasidim never took on an other rebbe. To this day, Rebbe Nachman is still the rebbe of the Breslavers.)

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[1] Photo by Shlomo Meir of the News 24 agency.
In the center is Rabbi Shalom Arush, a renowned modern-day teacher of Breslav Hasidut, especially “hitbodedut” — personal prayer.
From:
http://www.israelnationalnews.com/News/News.aspx/148425

[2] http://nanachnation.org/inspiration/uman-rosh-hashana/gclid=CNS9wcHL7M4CFYtahgodAU4COg