Tajug seen here on the roof of Wustho Mangkunegaran Mosque, Surakarta
Tajug is a pyramidal or pyramid square (i.e. an equilateral square base with a peak) ornament which is usually used for sacred buildings in Southeast Asia including Indonesia, such as mosque or cupola graveyard. It is considered derived from Indian and Chinese architecture, which has history since pre-Islamic era, although there's also an element of an influence from Indian mosques. The term tajug is also used to refer to mosques or surau (Islamic assembly building) in some regions of Indonesia.