Monumental Coins, those coins portraying monuments, are very popular with collectors.  Some of the greatest monuments of ancient time are only preserved on the coinage of the time.  Severus Alexander had some outstanding monumental coins.   Below are examples of these coins.

Obverse:  Laur., dr., & cuir., bust r.  Reverse:  Large altar, surmounted by eagle above which, Helios in facing quadriga; on l. of altar, tree.  Lindgren 17A (this coin); Price & Trell 163; Monumental Coins page 72. 227/228 AD.

In the book Monumental Coins by Marvin Tameanko  (a great book, I'd highly recommend), Tameanko describes the same coin only for the year 226-227 AD.  On page 72 he writes:  "This coin is a bronze, 38 millimeters in diameter, struck at Amasia in Pontus under Severus Alexander in 226-227.  See Sear GIC 3275.    The reverse is described as a large altar, surmounted by an eagle, above which appears Helios in a facing quadriga.   This building may have been a well-known, ancient shrine or tower-altar consecrated to Zeus.  The famous chariot at Gordium, according to legend, was erected by King Midas of Phrygia as a thank-offering to Zeus.   The yoke of this same chariot was tied with the puzzling Gordian Knot, which Alexander the Great supposedly unraveled by cutting with his sword."