Here's an ideal itinerary for 3 days in Toulouse:

Day 1:

Start your day with a visit to the iconic Basilique Saint-Sernin, one of the largest Romanesque churches in Europe. After that, head to the Musée des Augustins, which houses an impressive collection of medieval and Renaissance art. For lunch, try some local specialties like cassoulet or foie gras at one of the many restaurants in the area.

In the afternoon, take a stroll along the Canal du Midi, a UNESCO World Heritage Site that runs through the heart of the city. You can rent a bike or a boat to explore the canal further. End your day with a visit to the Place du Capitole, the main square of Toulouse, where you can admire the beautiful architecture and enjoy a drink at one of the many cafes.

Day 2:

Start your day with a visit to the Cité de l'Espace, a space-themed park that offers interactive exhibits, planetarium shows, and even a full-scale replica of the Mir space station. After that, head to the Jardin des Plantes, a beautiful botanical garden that features over 3,000 plant species from around the world.

For lunch, head to the Marché Victor Hugo, a bustling indoor market that offers a wide variety of fresh produce, meats, cheeses, and other local delicacies. In the afternoon, visit the Musée Saint-Raymond, which showcases the history of Toulouse from ancient times to the Middle Ages.

End your day with a visit to the Pont Neuf, the oldest bridge in Toulouse, which offers stunning views of the Garonne River and the city skyline. You can also take a boat tour of the river to see the city from a different perspective.

Day 3:

Start your day with a visit to the Musée des Abattoirs, a contemporary art museum that features works by artists from around the world. After that, head to the Musée Georges Labit, which houses a collection of Asian and Egyptian art and artifacts.

For lunch, try some delicious street food at the Marché des Carmes, a popular outdoor market that offers a wide variety of local specialties. In the afternoon, visit the Fondation Bemberg, a private museum that showcases a collection of European art from the Renaissance to the 20th century.

End your day with a visit to the Canal de Brienne, a picturesque waterway that connects the Garonne River to the Canal du Midi. You can take a leisurely walk along the canal or rent a boat to explore further.