The Islamic State has claimed responsibility for the June 7 attacks on Iran's parliament and a shrine for the nation's Islamic revolutionary leader. (The Washington Post)

Today, Islamic State terrorists attacked two major sites in Iran, killing at least 12 people and wounding scores more. One of the assaults targeted the country's parliament. The other took aim at one of the most sacred sites in Iran: the holy shrine of Ayatollah Ruhollah Khomeini, described as one of the “grandest architectural endeavors of  the Islamic Republic.

The expansive complex is “a spiritual and political testament to the 1979 Islamic revolution.” And an assault on the shrine — akin to a bombing at America's Tomb of the Unknowns — is an attack on the country's political identity and on one of Iran's most important monuments to Shiite Islam. As Marc Martinez, a senior analyst and Iran expert at the Delma Institute in the United Arab Emirates, explained to my colleague, today's attack is an assault on the Islamic revolution itself. As a result, he said, the choice of target may bolster the country’s strong sense of nationalism.

Police officers at the shrine of the late Iranian revolutionary founder Ayatollah Ruhollah Khomeini after an earlier terrorist attack. (Ebrahim Noroozi/AP)

The shrine's importance stems, in large part, from Khomeini himself. In the 1960s, Khomeini was one of the staunchest opponents of the ruling shah and the West. He was arrested and exiled to Turkey in 1964. He subsequently moved to Iraq, where he lived for 13 years, and spent nearly four months outside Paris before returning to Iran shortly before the shah's government collapsed in February 1979.

After his arrival on Feb. 1, 1979, Khomeini delivered a major public speech at the Behesht-e Zahra cemetery, the eventual site of his shrine, which had become closely associated with opponents of the shah's regime. Many of the people killed during the anti-shah protests of 1978 are buried there. In November 1979, a new constitution, under which Khomeini became Iran's "supreme leader," was approved in a landslide vote.

It was Khomeini who declared Iran an Islamic republic, introducing Islamic law across the country and denouncing America.

When Khomeini died on June 3, 1989, construction of the shrine began in earnest. At his chaotic funeral, millions of inconsolable mourners repeatedly stopped his hearse from moving toward the cemetery. Eventually, the crowd took hold of the coffin and began passing it over their heads. When the body fell out, the masses descended, trying to tear pieces of the shroud to keep as holy relics.

Mourners reach out to the body of Iranian leader Ayatollah Ruhollah Khomeini during his 1989 funeral ceremony. (Associated Press)

Today, the shrine is huge — the size of Heathrow Airport's Terminal 4. The property includes a gigantic courtyard and several buildings, along with the cemetery. More than 12,000 carpets cover the floors. Khomeini's tomb is covered with a stainless steel zarih, through which pilgrims can pay their respects. Someday, thousands of mirrors will adorn the ceiling.

Nearly every architectural feature is freighted with symbolism. Two 91-meter towers flank the shrine. The massive central dome is golden and adorned with 72 tulips, to symbolize the 72 martyrs who fought at Karbala in 680 A.D., a pivotal moment in the formation of Shiism.

The shrine of the late Ayatollah Ruhollah Khomeini at Khomeini's mausoleum in Tehran. (Atta Kenareatta/AFP)

The facility also houses many of the soldiers killed during the Iran-Iraq war. The ayatollah's wife is buried in the complex as well, along with several notable political figures. In 2017, former Iranian president Ali Akbar Hashemi Rafsanjani was interred there.

Today, visitors flock to the mausoleum, particularly during Ramadan. Every June, hundreds of thousands of mourners visit to mark the anniversary of Khomeini's death. In the month after Ramadan — Muharram — the fountains surrounding the shrine flow with water dyed red.

Thousands of Iranian worshipers attend the ceremonies marking the 15th anniversary of the death of Ayatollah Ruhollah Khomeini. (Abedin Taherkenareh/EPA)