See that mountain in the distance in the above Borobudur photo?
It's actually a volcano...
...and an active one at that! :O
When you look at the giant, multi-tiered monument to Buddhism that is Borobudur, it seems like its existence is hard to not notice. But for much of its history, the largest Buddhist temple in the world actually was covered -- and therefore hidden from view -- by layers of jungle growth and volcanic ash.
Built in the 9th century AD, Borobudur is thought to have been abandoned after a series of volcanic eruptions led area rulers to move their kingdom's capital from Central to East Java as well as the conversion of the Javanese to Islam in the 14th century. Recovered from nature in the 19th century, this cultural treasure has continued to come under threat from nearby volcanoes, at least one of which remains very active.
For example, as recently as 2014, it was covered by volcanic ash spewed by Mount Kelud. Even more dramatic by the sound of things was the violent series of eruptions in late 2010 from Mount Merapi which covered Borobudur with three-centimeter-thick ash (as well as resulted in 324 human fatalities).
One of 16 volcanoes in the world designated as Decade Volcanoes (which have a history of large, destructive eruptions, and are located in close proximity to populated areas), Mount Merapi is visible from Borobudur on a fine day (as well as the road leading to it from Yogyakarta airport, which my German friend and I flew into and out of on our recent Indonesian trip). Very formidable looking, I also actually think it's beautiful -- physically resembling Japan's much adored Fujisan, albeit minus the cone of snow at its top and with the addition of plumes of smoke coming out of it (that, thanks to my camera's zoom lens, I could clearly see as well as capture images of!).
On our car ride from Yogyakarta airport to our hotel in the grounds of Borobudur, the driver casually informed us that there are some six volcanoes in the area, including obviously very active ones like Merapi (whose name, appropriately enough, translates into English as "Fire Mountain"). And I'd be telling a lie if I didn't say I wasn't completely unworried after finding out that Java, and the nearby strait between it and Sumatra is home to 45 active volcanoes, including the infamous Krakatoa (which actually lies west of Java rather than east, like a film's title infamously mis-asserted)! ;S