“Angkor Thom” is sometimes spelt “Angkor Tom”. The name “Angkor Thom” has been used only after Angkor was not the Khmer capital any more, it means "Angkor Big" or "Capital Great". It was the last capital in the Angkor era. After Jayavarman VII recaptured the Angkorian capital from the Cham invaders and became king in 1181, he began a massive building campaign across the empire, part of it was constructing Angkor Thom as his new fortified capital. One inscription found in the city refers to Jayavarman as the groom and the new capital as his bride.
There had been previous cities covering some parts of what became now Jayavarman's new capital. Even parts of the first city established in Angkor, Yashodharapura, founded in the late ninth century, stretched into this area of Angkor Thom. Furthermore, the capital of Surayavarman I and Udayadityavarman II in the eleventh century had almost the same centre as the new city founded by Jayavarman VII. This is why their former state temple Baphuon, dedicated to Shiva, is located very close to Jayavarman's new Mahayana Buddhist state temple, Bayon, in the centre of Angkor Thom. A Royal Palace already existed just north of the Baphuon and was now used as residence by Jayavarman VII, who added the magnificent platform called terrace of the elephant.
There are five entrance gates to the city Angkor Thom, one for each cardinal point, the fifth being the Victory Gate only 400 metres north of the East Gate. From here the Victory Avenue led westwards and ended exactly in front of the Elephant terrace and the Royal Palace. This means, four symmetrically arranged city gates are lined up to the sacred centre of Angkor Thom, the Bayon temple, whereas the Victory Gate is in line with the secular core of Angkor Thom.
Angkor Thom is a square of walled up embankments of three kilometres length on each side. Laterite walls are supported on the inside by an enormous earth embankment. The city wall is surrounded by a gigantic moat, which ist 100 metres wide. At the corners of the city walls are small cruciform temples called Prasat Chrung. Because of their remote location they are untouristed, but quite nice. As mentioned, some already existing buildings were integrated into the new capital, such as the Phimeanakas inside the enclosure of the Royal Palace and the nearby Baphuon. Furthermore, the Khleangs from the tenth century and some Preah Pithu temples from the Angkor Wat period in the first half of the twelfth century already existed. Interestingly, another Hindu temple, called Western Prasat Top or Monument 486, was altered and now became a Buddhist sanctuary.
Jayavarman VII probably also founded or changed Preah Palilay and Tep Pranam just north to the Royal Palace. On the opposite side of the palace and elephant terrace, on the western side of the huge Victory square for festivals and parades, he erected the twelve towers of Prasat Suor Prat (sometimes they are supposed to be from an earlier period). Jayavarman VII is recognized as the most prolific builder in Angkor's history. Many more temples outside Angkor Thom were built by him, too, most of them earlier on, such as the huge complexes of Banteay Kdei, Ta Prohm, and Preah Khan. Furthermore, he founded hospitals and resthouses all over the empire and huge temple complexes in other areas as well, such as Banteay Chhmar, Preah Khan Kampong Svay and Ta Prohm Tonle Bati.
At the time that Angkor Thom was built, it was grander than any city in Europe. But it's secular buildings were made of wood and other perishable materials, this is why they do not exist any more. Today the largest parts of Angkor Thom are thicket and jungle.
Angkor Thom remained to be the Khmer capital until it was shifted to the south-east in the late medieval times. This means, from Jayavarman VII onwards, all Angkor kings resided in Angkor Thom. The successors finalized or modified some of the buildings, but there are only few examples of completely new constructions begun after the death of Jayavarman VII. Maybe Preah Palilay or parts of it are younger. A very small structure called Mangalartha or East Prasat Top or Monument 487, located close to the Victory and the East Gate, is from a later date, and probably it is the last stone building of Angkor. It was dedicated in 1295.
The best time to visit Angkor Thom's main attractions is the very early morning, before first bus groups arrive after hotel breakfast.
You need a ticket to enter the area between Angkor Wat and Angkor Thom when arriving from Siem Reap. Theoretically, you could enter Angkor Thom on tracks across the field from the west and the northwest. It would not be detected, but such a behaviour can not be recommended. Anyway, tickets are checked at the access points of the Bayon and of the Baphuon.