The little baroque garden in front of the Ossolineum is a peaceful and pleasant spot to sit down and rest in the middle of your sightseeing. It is surrounded by walls, hence a bit secluded, but the gates are open both from ul. Szewska and from the small lane between the church of St Mathias and the Clarisse abbey. The garden is free to enter.
Both the garden and the baroque facade have been beautifully restored. The garden is typically baroque, no flowers but low boxwood hedges and coloured pebbles in ornamental design. A closer look reveals that the pattern are actually musical keys (not typically baroque, admittedly). There are some benches, a couple of sculptures, and a little fountain which turns on the spot and is much loved by children.
The gates stay open until late at night, not sure if all night, but if you are looking for a romantic spot in the evening with your beloved, then here it is.
Ossolineum is a beautiful Baroque palace, built between 1675 and 1715, that once housed the Jesuit school, part of the Leopoldine University. Today, this red building on the Odra hosts the National Library, founded by Count Ossoliński in L'viv.
You should not miss it! I think it is one of the most beautiful buildings apart from those of the Rynek.
The Ossolineum Institute hosts one of the largest scientific libraries in Poland, special interest being laid on Polish and Slavonic history, culture and literature, a publishing company and a museum/gallery. It origins in Lemberg/Lwow and was transferred after 1945 to Wroclaw - unfortunately not completely; the larger part of the collections is still in the Ukraine.
The institute was founded by Józef Maksymilian Ossolinski (1748-1826), a writer, collector and scholar in Lemberg/Lwow in 1817 when he handed over to the Polish nation valuable collections of books, manuscripts and museum pieces.
As a tourist you're not entitled to use the library or see the main reading room - you need to subscribe to the library for that. However, sometimes (like when I visited) there are exhibits in the Ossolineum which you can see. I was so lucky to see a small but very nice exhibit (free) of Dürer and Rembrandt drawings/prints contrasted with modern pieces of Polish artists. But even if there are no exhibits then don't hesitate to enter the building and see the two quiet courtyards (see pictures) and admire the beautiful 17th century Baroque architecture (originally a hospital) after plans of Jean Baptiste Mathey from Burgundy.