Complex sentence: Some of these towers are permanently free of charge accessible, some have permanent entrance over a spider, where the admission fee is to be paid, others are accessible only at certain times as a rule only against payment of an admission fee.
Split into simpler sentences: Some of these towers are permanently accessible, either free of charge or over a spider, where the admission fee is paid. Others are accessible only at certain times, in most cases only against payment of an admission fee.