The Tropaeum Traiani is a monument in Roman Civitas Tropaensium (site of modern Adamclisi, Romania), built in 109 in then Moesia Inferior, to commemorate Roman Emperor Trajan's victory over the Dacians, in 102, in the Battle of Tapae. The monument was erected on the place where legio XXI Rapax had previously been defeated in 92. Before Trajan's construction, an altar existed there, on the walls of which were inscribed the names of the 3,000 legionaries and auxilia (servicemen) who had died "fighting for the Republic". (Latin: Tropaeum from Greek: Tropaion, source of English: "trophy").
Trajan's monument was inspired by the Augustus mausoleum, and was dedicated to the god Mars Ultor in 107/108 AD. On the monument there were 54 metopes depicting Roman legions fighting against enemies; most of these metopes are preserved in the museum nearby. The monument was supposed to be a warning to the tribes outside this newly conquered province.
The original monument has long since disintegrated. The present edifice is a reconstruction dating from 1977. The nearby museum contains many archaeological objects, including parts of the original Roman monument. Of the original 54 metopes, 48 are in the museum and 1 is in Istanbul.
(taken from http://en.wikipedia.org/wiki/Tropaeum_Traiani)