Tana is surrounded by the "twelve sacred hills of Imerina", the hilltop villages of the old Merina clans before they became a single kingdom. Some of these sites have been obscured by modern developments, but one, the UNESCO World Heritage Site of Ambohimanga Rova, is a significant and fascinating historical site and well worth a half-day trip (or longer). Although less well-known than the Rova in Antananarivo, it is in many ways more impressive, as it preserves intact some of the original eighteenth-century structures and brickwork of King Andrianampoinimerina, and there are tremendous views of the surrounding countryside and the northern suburbs of Tana.
Ambohimanga, now heavily forested, was originally one of four embattled Merina regional capitals, embroiled in a war of succession that lasted most of the eighteenth century. Only with Andrianampoinimerina's military success in capturing the Rova in Tana from this stronghold was the empire united and most of Madagascar subdued under Merina rule. To this day, Ambohimanga is the Merina's spiritual capital, but the physical integrity of the site, subject to rain erosion and cyclone damage (Cyclone Giovanna caused great destruction here in 2012, uprooting trees and lifting roofs) is under constant threat.
The hilltop site itself is an oval rova (hill fort), about 1km in length and 500m across, with the old earthworks and wall foundations of three distinct historical eras still discernible among the trees. Three of the original fourteen gateways are intact, and preserved alongside them the gigantic stone discs that at one time were rolled into place to seal the compound. The biggest of these, at the main Ambatomitsangana gate in the southwest, weighs about twelve tonnes.
Inside the rova, the oldest of the three compounds is Bevato, dating from the early eighteenth century. Higher up, the compound of Mahandrihono contains a number of restored houses, tombs and brightly painted royal pavilions. Above the other two compounds, Nanjakana, now largely overgrown, was the last to be constructed at the end of the eighteenth century.