The garden was located in a large agricultural area immediately north of the walls of the city of Baghdad, about 450 metres (1,480 ft) from the city's northern Mu'azzam gate. Located on the eastern bank of the Tigris River in what is now the Bab al-Mu'azzam neighbourhood of Baghdad's Rusafa District, it was directly opposite the district in which Bahá'u'lláh lived during his stay in the city, on the river's western bank. [Wikipedia]

Extract from a Tablet of Baha'u'llah-Khadimu'llah. (Edited provisional translation below)

"On the first day that the Ancient Beauty occupied the Most Great Throne in a Garden which hath been designated Ridván, the Tongue of Grandeur uttered three blessed verses.
[1] The first of them was that in this Manifestation the use of the sword in holy war is put aside.
[2] Secondly, prior to the completion of a millennium any theophanological claim put forward by any person must be considered baseless. In this respect the year should be considered a complete year.
[3] Thirdly, the True One, exalted be His Glory, at that time manifested all the Divine Names upon all things.
"Verily, all created things were immersed in the sea of purification when, on that first day of Ridván, We shed upon the whole of creation the splendours of Our most excellent Names and Our most exalted Attributes". [Kitab-i-Aqdas para75 p47]

And the following choice verse was subsequently revealed but has been ordained to be of the same rank as the preceding three; namely, whatever personal designations are mentioned before the Face, whether living or dead, such have thereby attained the Presence of God by virtue of being mentioned by the King of Pre-Existence. [UCMERCED site]

Thirty–one days after Naw-Rúz, which in this year fell on 22 March, Bahá'u'lláh left His house for the last time and walked to the Najíbíyyih Garden, afterward known as the Garden of Ridván (Paradise). This garden was on an island in the Tigris River and belonged to the governor of Baghdad, Najib Pásha. The river has since changed its course and the island is now a park on the north bank of the Tigris. [RoB1p237-282; Commentaries on Three Major Tablets by John Kolstoe p15]
• See BKG168, GPB149, RB1:260–1 and SA234–5 for details of His walk.
• For the first time, He wore a tall táj as a symbol of His station. [BBD221; BKG176; GPB152]
• Bahá'u'lláh entered the Garden just as the call to afternoon prayer was being made. [GPB149; RB1:261]
• On this day Bahá'u'lláh declared His mission to a few of His disciples. [RB1:260, 262]
• On the afternoon of Bahá'u'lláh's arrival at the Garden He revealed the Lawh-i-Ayyúb (Tablet of Job) (also known as the Súriy-i-Sabr (Súrat of Patience), Madínatu's-Sabr (City of Patience) and Súrat Ayyúb for Hájí Muhammad-i-Taqíy-i-Nayrízí whom He surnamed Ayyúb (Job). He was a veteran of the battle of Nayríz. The Tablet praised Vahíd and the believers of Nayríz. [SA239; Tablet of Patience (Surih Íabr): Declaration of Bahá'u'lláh and Selected Topics by Foad Seddigh]
• He also revealed the Tablet of Ridván, an Arabic tablet beginning with "He is seated upon this luminous throne.... [SA239]
• ...and Húr-i-'Ujáb (The Wondrous Maiden). [SA239]
• ...as well as Qad atá Rabí'u'l-Bayán, ...The Divine Springtime is come.... [SA240]
• and an Arabic Tablet that begins...When the gladness of God seized all else. [SA240]
• 'Of the exact circumstances … we, alas, are but scantily informed.' [BKG173; GPB153]
• For such details as are known, see BKG173–5 and GPB153. iiiii
• For the import of the event, see BKG169–73; G27–35; GBP153–5.
• This initiated the holy day of the First Day of Ridván, to be celebrated on 21 April. [BBD196]
• This marked the end of the dispensation of the Báb and of the first epoch of the Heroic or Apostolic Age of the Bahá'í dispensation. [BBD72, 79]
On the same day Bahá'u'lláh made three important statements to His followers:
1. He forbade the use of the sword.
2. He stated that no other Manifestations will appear before one thousand years. This was later reiterated in the Kitáb-i-Badí' and in The Kitáb-i-Aqdas.
3. He stated that, as from that moment, all the names and attributes of God were manifested within all created things, implying the advent of a new Day. [RB1:278–80]

During the 12 days in the Ridván Garden Bahá'u'lláh confided to 'Abdu'l-Bahá that He was 'Him Whom God shall make manifest'. [CH82]

• See CH82–3 for the effect of this announcement on 'Abdu'l-Bahá.

Bahá'u'lláh's family joined Him in the Garden. [BKG175; RB1:281; SA235]
• This initiated the holy day of the Ninth Day of Ridván, to be celebrated on 29 April. [BBD 196]

Bahá'u'lláh left the Garden of Ridván.
• This initiated the holy day the Twelfth Day of Ridván, to be celebrated on 2 May. [BBD196]
• As He was about to leave He revealed a Tablet addressed to Áqá Mírzá Áqá in Shíráz. It brought relief and happiness to those who received it. [EB222]
• His leaving was accompanied by symbolic signs of His station: He rode a horse rather than a donkey and wore a tall táj. [BBD221; BKG176]
• See BKG175–6, GPB155 and RB1:281–2 for descriptions of the scenes that accompanied His departure.

  Bahá'u'lláh and His party arrived at Firayját, about three miles away on the banks of the Tigris. [BKG176]

• There they stayed in a borrowed garden for a week while Bahá'u'lláh's brother, Mirza Musa, completed dealing with their affairs in Baghdad and packing the remaining goods. Visitors still came daily. [SA235]
• One of the loyal followers who was left behind was Ahmad-i-Yazdi. He would later make the journey to Constantinople where he received a Tablet from Bahá'u'lláh. [C3MT17]

"As of Riḍván 1997, all Local Spiritual Assemblies throughout the world will have to be elected on the First Day of Riḍván." (31 December 1995 – To the Bahá'ís of the World)

"This development was related to the fact that, while believers from outside a locality could assist with the electoral process, the primary responsibility for electing any Assembly and maintaining its operations rests with the Bahá'ís of that place" (30 December 2021 – To the Conference of the Continental Boards of Counsellors)