This article is specific to the outside areas of the Hogwarts campus. The campus itself is divided into east and west halves by a thin yet deep gorge. There is a suspension bridge, a wooden bridge, a viaduct bridge, and a thin double-tier tower bridge that connects the two sides.
Astronomy Tower and Turris Magnus
Location: Above the Defense Against the Dark Arts tower, south side of the west complex
In Hogwarts Legacy, the Astronomy tower and the Turris Magnus defensive tower are combined. The upper five floors of the Astronomy tower contain platforms instead of "floors" and have a three-story open-air window that allows students to use their telescopes to gaze unobstructed at the night sky looking east. There is also an observation deck that allows Astronomy students to gaze west.
Boat Slip
Location: On the Black Lake leading up to the viaduct courtyard via a long winding stairwell.
This location is confirmed during the gameplay reveal trailer. In it, we see a time-lapse day night cycle and the docks are clearly visible on the left-hand side of the screen. In Harry Potter canon, first-year students arrive to the school via boat from Hogsmeade Station, which is positioned directly across the Black Lake to the north. It is a large slip that can accommodate a single large ship.
Clocktower
Location: South part of campus across the bridge from the Gryffindor Dormatories.
This is the confirmed location for the Crossed Wands dueling club. The ground floor is where the dueling happens while the upper part of the building contains the complex workings of the clock itself. There are two bridges that connect the clocktower to the eastern side of the campus.
Defense Against the Dark Arts Tower
Location: Southern wall of west complex
This area consists of multiple "towers", including the Astronomy tower. The Defense Against the Dark Arts (DADA) tower is the building that you enter when crossing the suspension bridge from the east complex. It contains, among other things, the DADA classroom.
Forbidden Forest
Location: West of campus past the Quidditch arena
An expansive forest full of large, old-growth trees and small patches of marsh. The forest is aglow with various insects and magical effects.
Gamekeeper's Hut
Location: At the bottom of the hill just past the henge at the end of the clocktower's covered bridge on the south side of campus
Residence of the gamekeeper--whose job is to keep the game.
Gatehouse and Portcullis
Location: Between the Quidditch pitch and the quad
This is a classic castle gatehouse--complete with portcullis gate--which also contains a floo flame waypoint.
Greenhouses
Location: North side of campus built adjacent to the primary building on a cliff overlooking the Black Lake.
While the greenhouses probably have other utilitarian purposes that will become clear once the game launches, see "Hogwarts, Interior => Classrooms" for more details. There is a floo flame node directly outside of the entryway to classrooms I and II.
Hall of Herodiana
Location: the outside area between the chart room and the suspension bridge.
This area is completely outdoors despite being mostly under a roof. This area also contains a compass installed in the floor at the foot of the suspension bridge.
Owlry
Location: Atop a hill just south of the school
This is where owls are kept when not delivering messages. Sale of the guano helps the school keep tuition low. While walking around school, one of the students remarks that she's glad the owlry isn't connected to the school given how bad it smells.
Quadrillion
Location: Open ground between the gatehouse and the primary entrance of the school on the west side of campus.
Featuring hedges arranged in a circular patern, lantern lights for illuination at night, plants, and benches, this is a peaceful place for students to go and converse with friends. It is clearly the remains of a small bailey that was incorporated into the castle in its more knightly days. There is a massive fountain in the middle, adorned with animal heads representing each of the four Hogwarts houses.
Quad Courtyard
Location: Between the Great Stairwell tower, the Hall of Herodiana, and the Chart Room.
While normally you would expect a "quad" to have four sides, this three-sided "quad" has exits to the fountain above the Hufflepuff dormatories, the viaduct, and the Hall of Herodiana. There is an unlit brazier here, an Occamy statue, and several ramps.
Quidditch Pitch
Location: Outside of the school walls to the southwest.
This is the stadium where students, professors, and visitors can view matches of Quidditch--an airborne game where students attempt to score points by throwing balls through floating hoops or by catching an illusive flying ball known as a "snitch".
Ravenclaw Tower
Location: Center of campus attached to the east complex, immediately adjacent to the gorge
It has been determined that Ravenclaw house is located in its own tower of the school based on clues contained within the common room tour videos that were released during the Back to Hogwarts Day event. There is a connecting bridge between this tower and one of the two viaduct towers directly across the gorge. The upper level contains a dome skylight that lets in a ton of natural light into the space and the very top deck is an open-air observations area that connects to the Ravenclaw common room via spiral stairway.
Viaduct and the Viaduct Courtyard
Location: North side of Hogwarts next to the Black Lake.
This is a favored congregation area among the students. The viaduct (bridge) appears to contain a rotating brazier puzzle--though that has not been confirmed. There is a floo flame node located between the viaduct and the courtyard against the wall of the school.