The United Earth Embassy was United Earth's permanent diplomatic mission on Vulcan during the 22nd century. The United Earth Embassy was administered through the United Earth Diplomatic Corps, with officers from the United Starfleet serving in numerous operational and support positions. It was officially considered on Earth's soil by the Vulcans.
In 2154, Maxwell Forrest and Vulcan Ambassador Soval visited the Embassy to discuss the preliminary stages of joint missions between Earth Starfleet and the Vulcan High Command. In the course of this discussion, the embassy was bombed and badly damaged, killing at least forty-three people – including Admiral Forrest. The bombing was originally blamed on the Syrrannite movement, which the High Command characterized as a terrorist organization. It was later found that the embassy had been bombed by agents of Administrator V'Las, who sought to publicly discredit pacifist movements such as the Syrrannites as part of his plot to launch a preemptive invasion of the Andorian Empire. (ENT: "The Forge", "Awakening", "Kir'Shara")
Background information Edit
Presumably, this embassy served as the primary workplace for the United Earth Ambassador to Vulcan.
The script and production report for the Star Trek: Enterprise episode "The Forge", at wbm, established that the United Earth Embassy was in Shi'Kahr. This intention was also included at the bottom of a concept image that Senior Illustrator John Eaves created for the embassy. .
In the script of "The Forge", the exterior of the United Earth Embassy, when seen at night, was described thus; "Floodlit Human architecture jarring amidst traditional Vulcan structures."
The embassy's exterior was designed by John Eaves. He commented, "It really had to stand out so it went into a bright white surface color with a lot of cool architectural lighting to punch it out from the sea of red and purple that made up the Vulcan palette. Hard faceted and angular lines would also make for a good contrast against the very curvy organic lines all around the Embassy." 
In the script of "The Forge", the interior of the United Earth Embassy was stated to feature an "entrance hall" that was described as "a wide corridor that reminds us of Starfleet installations on Earth. A low-key security station at one end includes a console [...] and a small hand scan screen where people entering the Embassy place a hand to be identified." Evidently, the means of identification was ultimately changed to a retina scanner instead.
The interior of the embassy (at least in its undamaged state) was designed by Production Designer Herman Zimmerman. ("The Forge" audio commentary, ENT Season 4 Blu-ray special features) The embassy's interior was constructed on a basic structure for sets that had originally been made for depicting Cold Station 12, earlier in ENT Season 4. The embassy set included several reused set pieces. For instance, corridor walls in the area had additionally seen usage as elements of Cold Station 12, though they were originally built for a corridor aboard the USS Enterprise-J in ENT Season 3 offering "Azati Prime". Also, blue pillars in the embassy were originally made for the Romulan Senate in the film Star Trek Nemesis. They were built using faux marble. ("The Forge" text commentary, ENT Season 4 DVD & Blu-ray)
In the script of "The Forge", the embassy's exterior in its damaged state was described thus; "Ground Zero is a blackened scar in the Vulcan city..."
The embassy's destroyed junction room was scripted to be in a "sub-basement" of the building. This area was further described with the stage direction, "Fallen conduits, everything ruined." The contents of the room was scripted to include "a rubble-blocked doorway", an initially "non-operational" console, and "a mound of debris covered by a large fallen ceiling panel."
The wreckage of the United Earth Embassy was built as a different set from the one featured as the undamaged embassy. The creation of the embassy's remains as a separate set was deemed necessary. This was because both versions of the embassy were scheduled to be filmed on the same day and the undamaged version was soon thereafter redressed to appear as the Vulcan High Command; as a result, it wouldn't have been possible to convert the set fast enough to appear as the embassy wreckage.
The seemingly ruined interior was constructed on Paramount Stage 8, close to a set which was frequently used as the NX-class airlock. ("The Forge" text commentary, ENT Season 4 DVD & Blu-ray) The set included some fake stock monitors that had been made to seem as if they had been damaged; these monitors were built by members of the art department, including Denise Okuda. ("The Forge" audio commentary, ENT Season 4 Blu-ray special features) Some of the other bits of debris were recycled from season three, since the majority of Enterprise sets receive damage from Xindi attacks during the course of that season. Yet other parts of the embassy debris, such as some shattered concrete pillars, were created especially for inclusion in the ruins. One of the damaged walls was originally created for an auxiliary command center in "The Catwalk" and had most recently served as part of Dr. Arik Soong's laboratory in "Borderland". For its involvement in the detritus from the bombed embassy, the wall was extensively painted with scorch marks. Both this as well as dim lighting prevented the oft-reused piece from being recognizable. ("The Forge" text commentary, ENT Season 4 DVD & Blu-ray)
The design of the set for the United Earth Embassy, as the interior looks prior to being blown up, was highly popular with production staff members, including Denise Okuda and Judith Reeves-Stevens. Michael Okuda likewise found the embassy's blue "marble" columns to be "beautiful." ("The Forge" audio commentary, ENT Season 4 Blu-ray special features)
The United Earth Embassy presumably also included the office of the United Earth Ambassador to Vulcan, though, curiously, no such individual is mentioned meeting with the crew in the episodes.