From the Super Mario Wiki
Luigi enters the Courtyard after defeating Bogmire. When he first enters, Flying Fish and (despite there being no ceilings) Ceiling Surprises and Purple Bombers attack him. After Luigi captures them, the lights turn on. A Toad is nearby in an old cabin. This Toad saves Luigi's progress and tell him to go to the Bottom of the Well. On the way, Luigi inspects a birdhouse, which spits out Mario's Letter.
The Courtyard has many crooked dead trees spread troughout it. Then (from left to right) there is a statue that looks like Slim Bankshot, a large fountain with plants surrounding it (the plants can be watered for money and hearts), a well, a birdhouse, an old cabin, and another statue. After Luigi visits the Bottom of The Well and goes back up, he hears Mario saying "Hey, Luigi! What's the hold-up?" very faintly.
Ghosts in The Courtyard
Ghosts in The Courtyard during the blackout