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Set post-Martha, the doctor is travelling with Donna. Spoilers: Early season three. I have only seen half-way through season three, so apologies for any inconsistencies.
The Tardis shuddered to a halt, throwing the Doctor and his new companion roughly to the floor.
"Blimey! You call that a landing?" Donna carefully picked herself up off the metal grating and inspected her arms for bruising.
"Right, here we are then!" The Doctor, ignoring Donna's jibe, bounced across the room to snatch his coat off a nearby railing. "Tielaran! Settled by humans in the year, oh, eighteen thousand for a scientific study of the uninhabited planet, quickly turned into a refuge for endangered species, and now, in the year Nineteen thousand and fifty-six, Teilaran boasts the largest zoological collection of rare animals in the galaxy. It's said that the settlement has saved thousands of species from extinction, hear that Donna? Thousands! I expect that that's mostly exaggeration, but you have to admit, their reputation is very impressive. Donna? What? Stop looking at me like that." As the Doctor stood by the Tardis doors, Donna remained by the consol, arms folded, wearing a stern expression.
"I want your word, Doctor."
"What about?"
"You said a quiet trip, to a peaceful colony. No monsters, no mortal danger, no running for my life. Before I walk out those doors I want your word on that." Donna's expression spoke volumes. She did not want an adventure today.
"It's basically a zoo, Donna. What could possibly happen?"
Donna raised her eyebrows.
"Alright, I promise. Can we go now?" The Doctor was practically bouncing with impatience.
Donna rolled her eyes as she joined him by the doors. "Just for the record, I don't believe you. So when we get into trouble, I get to say 'I told you so'."
"Statement acknowledged." The Doctor put his hand on the door. "Donna, I give you: Tielaran."
Donna stepped through the opening door and gaped at the sight that greeted her. Whatever trouble they got into, it would be worth it.
"Doctor, it's…beautiful."
She heard the Tardis door close gently as the Doctor joined her side.
"I thought you'd like it." He sounded pleased with himself. Donna didn't mind.
They stood on a green hill beneath a clear, blue sky. The sun shone directly overhead, not harsh, merely pleasant. The air smelt of flowers and grass, and a magnificent forest stretched out to the left and right of them. But none of this compared to what lay directly ahead of them, just far enough away that Donna could take it all in at once. A white stone wall surrounded what looked like a city, with buildings of the same stone clustered within the wall, but the whole city was dominated by a huge white dome, impossibly large, tiny windows could just be made out against the glare of the sun reflected off the gleaming stone. It reminded her of the Taj Mahal, with reflected sunlight instead of gold.
"That dome," the Doctor spoke in her ear, "contains thousands of endangered species, both terrestrial and alien, brought here to ensure their survival, and, if possible, to be later reintroduced back to their home planet."
"And we can see them?" Donna asked him, a grin playing about her mouth.
"We can see them." The Doctor confirmed, smiling like the stars had come out.
"Well, what are we standing here for? Come on!"
Donna grabbed the Doctor's hand and set off at a run down the hill, towards the great, white city.