Several Shia Imams are buried in Iran. Conversely Sunnis have been terribly persecuted during the Shia dynasties in Egypt, North Africa,Sicily, Spain, Arabian Peninsula, Syria and Iraq, Iran & Azerbaijan.
The Mongols hordes burned and razed to the ground all mausoleums, museums, institutions of learning and research, big buildings, mosques and libraries.. Baghdad was turned into a ghost city with river Tigris full of books and the human blood for miles.
The unity of Muslims as one nation would always remain a myth and unattainable goal. The bridging of the doctrinal and theological chasms between these two main sects within Islam would always remain a tall order unless the Muslim clergy of both the sects reconcile on living in harmony despite their mutual differences of faith and Sharia laws. Would that be possible within an Islamic state cannot be fathomed.