建於1933年的發達堂，不但見證區內一個顯赫的客家家族的歷史，亦是折衷主義住宅建築的典型例子，這種建築風格廣為香港20世紀初期海外歸僑所採用。
發達堂由「李道環祖」（由李道環四個兒子組成的受託人）在新界沙頭角下禾坑興建；李道環是禾坑李氏宗族的後裔。正如沙頭角許多在19世紀末遠赴海外謀生的年輕人一樣，李道環年輕時前往越南謀生，後與家人衣錦還鄉，在下禾坑定居。
李道環的長子李鈞蘭是沙頭角區內舉足輕重的社區領袖，於1936年獲總督委任為沙頭角區三名「諮議」之一，負責就區內事務和糾紛提供意見。當時獲總督委任為「諮議」被視為莫大的榮譽。
發達堂樓高兩層，建有長長的客家式人字瓦頂，正面是平頂柱廊陽台，其頂部是裝飾欄杆，就像滾滾的雲朵。建築物以傳統的青磚和木材，以及現代的鋼筋混凝土建成。為加強保安，大宅所有正門均設金屬製的中式趟櫳門，樓下多排窗戶亦裝有金屬窗罩。該建築包含 5 間相互連接的房屋，每間房屋在地下都有獨立的門口。時至今日，發達堂仍是李道環後人的居所。
發達堂於2010年被評為一級歷史建築，2013年被列為法定古蹟。
Fat Tat Tong, built in 1933, is not only a testimony of the history of a renowned Hakka family in the area, but also a typical example of residences of eclectic style popular with the returned overseas Chinese in the early 20th century in the territory.
Fat Tat Tong was built by Li To Wan Tso, a trustee formed by the four sons of Li To-wan, in Ha Wo Hang, Sha Tau Kok, New Territories. Li To-wan was a descendant of the Li clan of Wo Hang. Like many young adults of Sha Tau Kok going abroad to make a livelihood in the late 19th century, Li To-wan went to Vietnam to earn a living at a young age. He and his family returned to Ha Wo Hang with a modest fortune.
Li To-wan’s eldest son, Li Kwan-lan, was an influential community leader of Sha Tau Kok and was appointed as one of the three “Tsz Yi” of Sha Tau Kok District in 1936 by the Governor to give advice on matters of local affairs and disputes. The appointment of Tsz Yi was regarded as an honorary offer of the Governor at the time.
Fat Tat Tong is a 2-storey residence with a long pitched Hakka style tiled roof and fronted by a flat-roofed colonnaded verandah which is crowned by an ornamental parapet that resembles a stream of rolling clouds. Traditional green brick and timber as well as modern reinforced concrete are used for the construction. Chinese-style sliding doors constructed of metal at all front entrances and rows of windows with metal hoods at the ground floor level are used to enhance the security of the building. The building contains 5 interconnected houses, each with its own entrance on the ground floor. Nowadays, Fat Tat Tong still serves as a residence for the descendants of Li To-wan.
It was rated a Grade I historic building in 2010 and a declared monument in 2013.
