Complex sentence: Near the Horse is an obelisk called the Lansdowne Monument, visible in some photographs of the White Horse; it is a 38-metre stone obelisk erected in 1845 by the 3rd Marquess of Lansdowne to commemorate his ancestor, Sir William Petty.
Split into simpler sentences: Near the Horse is an obelisk called the Lansdowne Monument, visible in some photographs of the White Horse. This is a 38-metre stone obelisk, erected in 1845 by the 3rd Marquess of Lansdowne to commemorate his ancestor Sir William Petty.