"Seven Men at Daybreak" is the title of a book by Alan Burgess. It tells the story of a group of Czech resistance fighters who were parachuted into then German occupied Czechoslovakia to kill Reinhard Heydrich, the SS officer who commanded occupied Czechoslovakia. A film "Operation Daybreak" was based on the book.
Inside the crypt itself, we saw a number of small wreaths and crosses left in memory of those who died there. The parachutists are still seen very much as heroes who died for the freedom of their country.
Note: the above account is based on memories of reading "Seven Men at Daybreak" (many years ago) and on the content of the displays in the museum at the crypt.