ThinkSPAIN said human towers, in which people stand on each other's shoulders, are a popular feature of local festivals, and are usually performed by trained gymnasts or dancers.
The Vida de Gracias fiesta association's human tower involved eight levels, with five people per level and extra people on the ground for support.
The tower collapsed during a display Sunday in Barcelona, and a man hit the ground and passed out.
The man is undergoing tests, ThinkSPAIN reported.
Doctors said they are not releasing further information to protect the man's privacy.
The regional coordinator of human towers said the falls are very rare.