Abu Musa Island is strategically located in the bottleneck of the Strait of Hormuz. Since the 1980s, Iran has installed launch pads for advanced anti-ship missiles on the island. [1] According to Jane's Defense Weekly, "the launchers and associated radar for these missiles are probably housed along the north end of the island, where satellite images depict a number of revetments (possibly lined with concrete) forming a tunnel around a large hill." [2] However, Iran is believed to keep most of the missiles in storage onshore, ready for deployment when needed.[3] The Asia Times has also reported Iranian deployment of supersonic cruise missiles such as the Yakonts, Moskits, Granits, and Brahmos on Abu Musa. [4]

Sources:
[1] David Eshel, "Hormuz Straits Come Into Focus as Gulf Tension Mounts," Defense Update, 19 April 2007, www.defense-update.com.
[2] Clifford Beal, "Uncovered: Iran's Abu Musa Island," Jane's Defence Weekly, 8 March 2000, www.janes.com.
[3] David Hartwell and Allison Puccioni, "Island Fortresses - Abu Musa and Greater Tunb," Jane's Intelligence Review, 14 August 2009, www.janes.com.
[4] Victor N. Corpus, "Part I: Striking the U.S. where it Hurts," Asia Times, 19 October 2006, www.atimes.com.