For a time, Asunción was an important city to the Spanish colonial administration. It was an easier sail from Spain: across the Atlantic, up the Río de la Plata, hop over to the Río Paraguay and use the growing port as a staging area to the rest of the South American heartland. Asunción developed along the river bank. To the east of the river, fertile land supported the growing population and the city thrived. Buildings from the colonial period attest to the prosperity of the city the Spanish enjoyed as almost a vacation resort.
Currently, much of the historical section with its charming colonial buildings and plazas is near the river and is easily walkable. You should see some interesting constructions like: Panteón Nacional de los Héroes, characterized by its pink dome; Casa Viola, which was renovated and is a prime example of early colonial architecture; Casa de la Independencia, where revolutionaries met in secret to plan their battle for independence, houses relics from the 1811 revolution; Catedral Metropolitana dated from 1687 and notable for the very large gilded altar and religious art. The city also has a mild climate for most of the year except the summer months (October to March) when you should avoid touring in mid-day.