Dome over the grave of Imam Ahmad as per Ibn Battuta

Dome over the grave of Imam Ahmad.
Ibn Battuta said regarding the grave of Imam Ahmad.
وبالقرب منها قبر الإمام أبي عبد الله أحمد بن حنبل رضي الله عنه ولا قبة عليه. ويذكر أنها بنيت على قبره مراراً فتهدمت بقدرة الله تعالى. وقبره عند أهل بغداد معظم، وأكثرهم على مذهبه.
The grave of Imam Abi Abdillah Ahmad bin Hanbal may Allah be pleased with him is near it. There is no dome over it and they say they made a dome over it various times but every time it was destroyed by the power of Allah. The people of Baghdad admire his grave and most of them are on his (Ahmad’s) Madhab. [al Rihla Ibn Battuta part 1 page 220]
Note: Ibn Battuta himself was a Sufi and mentioned everything he heard related to sufis and saints.