Alpera Castle, locally known as Castillo de Alpera or Castillo de San Gregorio, lies on a low hill west of the town of the same name, in the province of Albacete in Spain.
Not much is known about Alpera Castle. It is of Muslim origin and is said to have been built during the 12th century.
After these lands were reconquered by the Aragonese, in 1296, they were seriously depopulated. So in 1338 the area was repopulated again by Christians and the old Muslim castle of Alpera was then rebuilt on the orders of Don Juan Manuel.
The castle had an oval shape. There are remains of a Muslim tower built out of rammed earth and 4 Christian towers built out of dressed stones. The top of the hill is now empty.
At present the remains of Alpera Castle can freely be visited. There is almost no architectural detail to be seen, so not very interesting.