Ghosts, crimes, and spooky legends are the basis for the Buenos Aires Misteriosa tours by Ayres Viajes, which also offers general tours in and around town.
The service—for tours in town and out—you get from Isabel at Buenos Aires Tours is almost heroic.
For a local's perspective, contact the Cicerones de Buenos Aires, a free service that pairs you with a porteño to show you parts of town you might not see otherwise.
Informed young historians from the University of Buenos Aires lead cultural and historical tours at Eternautas. It offers general city tours, themed private outings (e.g., Evita and Peronism, the literary city, Jewish Buenos Aires), and excursions outside town.
With La Bicicleta Naranja you can rent a bicycle and gear—delivered to your hotel—to follow one of the routes on their excellent maps or go with a bilingual guide on general or themed trips.
See Buenos Aires from the river on a 2½-hour sailboat tour with Smile on Sea.
What better way to explore the waterways of the Tigre Delta and Puerto Madero's docklands than from the water? Puro Remo is a rowing club that offers guided kayaking and rowing tours (no experience needed). 11/15–5808–2237. www.puroremo.com.ar.
Look down on the city and its surroundings from a helicopter, hot-air balloon, or glider on one of the aerial tours run by Buenos Aires Alternativo.
Large onboard screens make the posh minibuses used by Opción Sur part transport and part cinema. Each stop on their tours of the city and the Tigre Delta is introduced by relevant historical footage (e.g., Evita rallying the masses at Plaza de Mayo).
You get serious insight into the Jewish community on day tours run by Deb Miller's company, Travel Jewish.
See the major sights and get the lay of the land on the basic three-hour bus tours in English and Spanish run by Travel Line.
For tailor-made city tours, contact Wow! Argentina well in advance of your arrival in Buenos Aires. Enthusiastic Cintia Stella and her team also arrange excursions all over Argentina.