Tulum is the Mayan word for fence, trench or wall
and the walls surrounding the site allowed Tulum fort to serve as a
defense against an invasion. From the numerous depictions in murals and
other works around the site, Tulum appears to have been an important
site for the worship of the Descending god.
inscription dated 564 has been found at the site, most of the structures
now visible were built between about 1200 and 1450. The city remained
occupied through the early years of the Spanish conquest of Yucatán, but
was abandoned by the end of the 16th century.
While Tulum is only archaeologically mediocre (once you've been to Uxmal,
Chichen Itza and Tikal), I think it's one of the prettiest. The
stone cliffs along the azure sea are beautiful. As far as I know,
this is the only Mayan ruins of any significance found along any coast.