The higher elevations occur in the center of the island, west side of the ancient Portuguese colony, which is dominated by a massive central backbone, the Ramelau (of eruptive or metamorphic constitution), with chain ramifications that follow the axis of the island, either run towards the coasts, where in the north they can be seen stretching to the seashore (Fatu Cama for instance) or dropping abruptly into the sea (like in Subão) whereas along the south the slopes are more discrete and clear away at some distance from the sea, thus leaving a wide littoral strip of alluvial formations. To the East, the ruggedness of the relief softens but is uneven -- perhaps due to higher geologic complexity -- giving way to planaltic formations that are interrupted by characteristic steep cliffs (of metamorphic, calcareous-sedimentary, or eruptive nature). The natives call them "fatu", and after the geologists. Some are of great dimensions such as the Maté Bian massif west of Báguia and reaching 2 316 m at the peak of Boicau. Northwest of Ossu rises the imponent Lost World (1 763 m), and northeast of Venilale, from Fatu Laritame (1 220 m) parts the Cuac stream.
Now in the west side of East Timor, Ramelau ranges up to a height of 2 964 m at the peak of Tata-Mai-Lau. To the NW ramifies mountain Caterai (2 100 m), between Atsabe and Lete Foho, and towards SW Darulau (2 320 m) which separates Atsabe from Ainaro. In the direction of Same stands the Cablac (2 180 m), once considered by the indigenous as where reuned the souls of the dead. Still other mountains of around 2 000 m exist in the main territory.
The enclave of Ocussi-Ambeno, is also very accidented and irregular. In the NE corner, partially of recent volcanic constitution, can be seen the wildest and youngest relief of the entire island, which reaches 1 561 m at the border (Nipane peak). The volcanic island of Ataúro emerges very steeply from the sea, up to 999 in the mountain of Mano Côco, and is very mountainous.
The north side of the island is characterized by countless littoral terraces, of coral origin, and some extensive plateaus (in both cases of coral origin) at different altitudes -- 400 to 700 m -- such as those of Baucau, where was constructed an airport and Laga, and already mentioned Laga. There's a few alluvial formations between Lautém and Baucau and in the regions of Vemasse and Manatuto. The major plains are those of Batugadé, Lóis stream, Metinaro, Díli, Manatuto and Com.
The south coast forms almost entirely a wide plain, which extends from the frontier to Viqueque, and then more narrow until Loré, yet wider than the northern plains. The most important are in Alas, where serpentines the South Lacló stream, Quirás which is bathed by the Sahe in the rainy season, Luca that is watered by Dilor, and Bilibuto.
Frontier to West Timor in the inland lies still the important low plateau of Maliana which once was a golf.
During the rainy season, they are potent agents of erosion as intense precipitation originates strong torrents which drag away enormous quantities of waist and causes extensive alluvialment. But soon after the rain has stopped, as the level of the waters lowers, once more wading becomes possible. With the come-back of the dry winds of Australia, the water courses that survive resume themselves to a string of water that runs lost in a big stream bed full of wreckages and that keeps widening every year.
In some permanent courses along the south coast, the accumulation of sand at the mouth of the stream by the action of strong tides, turns drainage impossible, what leads to the formation of marshes. In it, fishes from the sea and crocodiles driven down stream continue to develop until the natives dig an exit (this is accompanied by a ritual in which fishes, shrimp, snakes and small crocodiles are caught by hand).
All streams are unnavigable, being helpless as a mean of communication. Quite on the contrary, they condition the economic relations: virtually unable to serve as a mean of penetration to the inland, for some months the torrents make communication impracticable between the fertile plains of the south coast and the consuming centers of he remaining territory. Besides they are also responsible for the deficiency of the streets. There's the need to cover the slopes with vegetation that retains the waters and forces them to penetrate in the soils at their passage, thus avoiding the destructive torrents.
The streams with permanent course appear in the south coast, where predominates a type D climate (that guarantees a longer rainy period), and in the north coast when it's water courses spring or receive affluents from the southern side. Those are the cases of the North Lacló, and the Lóis. This one constitutes the largest hydrographic basin of East Timor and the other is the longest stream, with 80 km, and discharges at Manatuto. To the south, Tafara, Bé-lulic, Carau-úlun, Sui, South Lacló and Cler also have water all the year round.
In the enclave of Ocússi-Ambeno the principal stream is Nuno-eno, which runs into the sea west of Pante Macassar.
The seabooards of both coasts are propitious for the formation of swamps after heavy rainfalls. Some lakes do occur, being the largest -- Suro-bec -- in the far east, measuring 6,5 km in lenght and 3 km of width. The others, of Maubara, and Tibar haven't any importance. The mountainous nature of the island favours still the existence of water falls of which the best known is that of Bandeira.
There are yet little contributions for the study of the streams of East Timor, and even controverse about their nomenclature, which sometimes is referred distinctly at the different regions crossed by the water courses.
The south coast of Timor, facing the Indian Ocean is constantly billowed by the Timor Sea, therefore struggling for navigation. Such is it's roughness that the Indigenous call it the "man sea" (Taci-Mane) in opposition to the "woman sea" (Tace-Feto) of the north coast, where it's already the Pacific Ocean waving on the shore through the Banda Sea.
There the waters are calmer, and quickly gain much depth (more than 1000 m at 5 miles off the coast). It was recently discovered that during the peak of the Cold War, American nuclear submarines passed through the Ombai and Wetar straits, which's depth assured undetectability. In the Timor Sea, the narrow but very deep Timor Trough (maximum of 3200 m) along the coast gives way to the shallow Sahul Shelf, once above sea level, and where Australian companies have oil explorations.
The best anchorage-ground of the island, is the bay of the capital Díli, sheltered by shoals of coral that leave two entries. More to the east deserve mentioning the ports of Lifau and Baucau for vessels of low draught. In the south coast, much less accidented there aren't but creeks of little importance like those of Suai, Alas and Luca. In the enclave of Ocussi-Ambeno, there's the Tulary Ican bay, although hardly guarded from the NW monsoon.