Fortification
Numerous Indus Valley Civilization sites exhibit evidence of fortifications. By about 3500 BC, hundreds of small farming villages dotted the Indus floodplain. Many of these settlements had fortifications and planned streets. The stone and mud brick houses of Kot Diji were clustered behind massive stone flood dykes and defensive walls, for neighbouring communities bickered constantly about the control of prime agricultural land. The fortification varies by site. While  Dholavira has stone-built fortification walls, Harrapa is fortified using baked bricks; sites such as Kalibangan exhibit mudbrick fortifications with bastions and Lothal has a quadrangular fortified layout. Evidence also suggested of fortifications in Mohenjo-daro. Even a small town—for instance, Kotada Bhadli, exhibiting sophisticated fortification-like bastions—shows that nearly all major and minor towns of the Indus Valley Civilization were fortified. Forts also appeared in urban cities of the Gangetic valley during the second urbanisation period between 600 and 200 BC, and as many as 15 fortification sites have been identified by archaeologists throughout the Gangetic valley, such as Kaushambi, Mahasthangarh, Pataliputra, Mathura, Ahichchhatra, Rajgir, and Lauria Nandangarh. The earliest Mauryan period brick fortification occurs in one of the stupa mounds of Lauria Nandangarh, which is 1.6 km in perimeter and oval in plan and encloses a habitation area.Mundigak (c. 2500 BC) in present-day south-east Afghanistan has defensive walls and square bastions of sun dried bricks. 

India currently has over 180 forts, with the state of Maharashtra alone having over 70 forts, which are also known as durg, many of them built by Shivaji, founder of the Maratha Empire.

A large majority of forts in India are in North India. The most notable forts are the Red Fort at Old Delhi, the Red Fort at Agra, the Chittor Fort and Mehrangarh Fort in Rajasthan, the Ranthambhor Fort, Amer Fort and Jaisalmer Fort also in Rajasthan and Gwalior Fort in Madhya Pradesh.
The Arthashastra the Indian treatise on military strategy describes six major types of forts differentiated by their major modes of defenses.

Sri Lanka: Forts in Sri Lanka date back thousands of years, with many being built by Sri Lankan kings. These include several walled cities. With the outset of colonial rule in the Indian Ocean, Sri Lanka was occupied by several major colonial empires that from time to time became the dominant power in the Indian Ocean. The colonists built several western-style forts, mostly in and around the coast of the island. The first to build colonial forts in Sri Lanka were the Portuguese; these forts were captured and later expanded by the Dutch. The British occupied these Dutch forts during the Napoleonic wars. Most of the colonial forts were garrisoned up until the early 20th century. The coastal forts had coastal artillery manned by the Ceylon Garrison Artillery during the two world wars.
Most of these were abandoned by the military but retained civil administrative officers, while others retained military garrisons, which were more administrative than operational. Some were reoccupied by military units with the escalation of the Sri Lankan Civil War; Jaffna fort, for example, came under siege several times.

China: Large tempered earth (i.e. rammed earth) walls were built in ancient China since the Shang dynasty (c. 1600–1050 BC); the capital at ancient Ao had enormous walls built in this fashion (see siege for more info). Although stone walls were built in China during the Warring States (481–221 BC), mass conversion to stone architecture did not begin in earnest until the Tang dynasty (618–907 AD). The Great Wall of China had been built since the Qin dynasty (221–207 BC), although its present form was mostly an engineering feat and remodelling of the Ming dynasty (1368–1644 AD).
In addition to the Great Wall, a number of Chinese cities also employed the use of defensive walls to defend their cities. Notable Chinese city walls include the city walls of Hangzhou, Nanjing, the Old City of Shanghai, Suzhou, Xi'an and the walled villages of Hong Kong. The famous walls of the Forbidden City in Beijing were established in the early 15th century by the Yongle Emperor. The Forbidden City made up the inner portion of the Beijing city fortifications.

Philippines: 

Spanish colonial fortifications: During the Spanish Era several forts and outposts were built throughout the archipelago. Most notable is Intramuros, the old walled city of Manila located along the southern bank of the Pasig River. The historic city was home to centuries-old churches, schools, convents, government buildings and residences, the best collection of Spanish colonial architecture before much of it was destroyed by the bombs of World War II. Of all the buildings within the 67-acre city, only one building, the San Agustin Church, survived the war.
Partial listing of Spanish forts:

Intramuros, Manila
Cuartel de Santo Domingo, Santa Rosa, Laguna
Fuerza de Cuyo, Cuyo, Palawan
Fuerza de Cagayancillo, Cagayancillo, Palawan
Real Fuerza de Nuestra Señora del Pilar de Zaragoza, Zamboanga City
Fuerza de San Felipe, Cavite City
Fuerza de San Pedro, Cebu
Fuerte dela Concepcion y del Triunfo, Ozamiz, Misamis Occidental
Fuerza de San Antonio Abad, Manila
Fuerza de Pikit, Pikit, Cotabato
Fuerza de Santiago, Romblon, Romblon
Fuerza de Jolo, Jolo, Sulu
Fuerza de Masbate, Masbate
Fuerza de Bongabong, Bongabong, Oriental Mindoro
Cotta de Dapitan, Dapitan, Zamboanga del Norte
Fuerte de Alfonso XII, Tukuran, Zamboanga del Sur
Fuerza de Bacolod, Bacolod, Lanao del Norte
Guinsiliban Watchtower, Guinsiliban, Camiguin
Laguindingan Watchtower, Laguindingan, Misamis Oriental
Kutang San Diego, Gumaca, Quezon
Baluarte Luna, Luna, La Union

Local fortifications: The Ivatan people of the northern islands of Batanes built their so-called idjang on hills and elevated areas to protect themselves during times of war. These fortifications were likened to European castles because of their purpose. Usually, the only entrance to the castles would be via a rope ladder that would only be lowered for the villagers and could be kept away when invaders arrived.

The Igorots built forts made of stone walls that averaged several meters in width and about two to three times the width in height around 2000 BC.
The Muslim Filipinos of the south built strong fortresses called kota or moong to protect their communities. Usually, many of the occupants of these kotas are entire families rather than just warriors. Lords often had their own kotas to assert their right to rule, it served not only as a military installation but as a palace for the local Lord. It is said that at the height of the Maguindanao Sultanate's power, they blanketed the areas around Western Mindanao with kotas and other fortifications to block the Spanish advance into the region. These kotas were usually made of stone and bamboo or other light materials and surrounded by trench networks. As a result, some of these kotas were burned easily or destroyed. With further Spanish campaigns in the region, the sultanate was subdued and a majority of kotas dismantled or destroyed. kotas were not only used by the Muslims as defense against Spaniards and other foreigners, renegades and rebels also built fortifications in defiance of other chiefs in the area. During the American occupation, rebels built strongholds and the datus, rajahs, or sultans often built and reinforced their kotas in a desperate bid to maintain rule over their subjects and their land. Many of these forts were also destroyed by American expeditions, as a result, very very few kotas still stand to this day.
Notable kotas:

Kota Selurong: an outpost of the Bruneian Empire in Luzon, later became the City of Manila.
Kuta Wato/Kota Bato: Literally translates to "stone fort" the first known stone fortification in the country, its ruins exist as the "Kutawato Cave Complex"
Kota Sug/Jolo: The capital and seat of the Sultanate of Sulu. When it was occupied by the Spaniards in the 1870s they converted the kota into the world's smallest walled city.

Pre-Islamic Arabia: 

During Muhammad's lifetime: During Muhammad's era in Arabia, many tribes made use of fortifications. In the Battle of the Trench, the largely outnumbered defenders of Medina, mainly Muslims led by Islamic prophet Muhammad, dug a trench, which together with Medina's natural fortifications, rendered the confederate cavalry (consisting of horses and camels) useless, locking the two sides in a stalemate.