Tajug seen here on the roof of Wustho Mangkunegaran Mosque, Surakarta.
Tajug is a pyramidal or pyramidsquare (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 cupolagraveyard. It is considered derived from Indian and Chinese architectural style which has history since pre-Islamic era, although there's also an element of an influence from Indian mosque. The term tajug is also used to refer to mosques or surau (Islamic assembly building) in some regions of Indonesia.