A spire was in architecture a conical or pyramidal structure, usually on top of a building. A spire could also be built separately, like a Bantaca spire, and had some similarities with an obelisk.
After defecting to the Federation in 2366, Alidar Jarok lamented that he'd never be able to see the spires of his home on Romulus rise above the Apnex Sea at dawn. (TNG: "The Defector")
On Ferenginar, a spire adorned the Tower of Commerce. In 2371, Quark feared that he and Rom would be brought to this spire and then thrown down to the Sacred Marketplace alongside Grand Nagus Zek, when Zek planned to announce the the revised rules of acquisition to the Ferengi population. (DS9: "Prophet Motive")
One year later, Brunt told the members of the Guild of Restaurant and Casino Employees of Quark's that on Ferenginar he'd have them all brought to the spire, displayed to the crowds below, and then shoved off one by one. (DS9: "Bar Association")